Seagrasses Established--I will add KNO3 and Fe

[monicaswizzle]

Well, Sarah, Clay, John and the other sea grass nerds must all be busy or off to doing other things, so I have decided without the benefit of their advice to start fertilizing my sea grass bed. In the interest of providing information for others that want to fool around with this, I will go into some detail and try to update with an occasional progress report. Sorry if the long post bores you--feel free to move on to something more fun.

If you have experience and it seems like I am doing something you know to be a bad idea--please let me know! Thanks.

My setup:

90 gallon display that overflows into a 50 gallon sump with moderate flow (600gph return pump, 5 koralias--three on wavemaker outlets and two on 24/7).

Display lighting is two 400 watt metal halides (and one 3 watt actinic that is on 24/7) that are on for 6 hours, off for two, back on for another 6 every day. Sump has NO lights and 6 watts actinic.

DSB--left 1/3 of tank is about 7" deep, right 2/3 is about 3 to 4". About equal parts "live" sand and "dead" sugar sand. 1 gallon of "miracle mud" added when first established (three plus years ago). Totally "rebuilt" in March , 2009, when tank cracked, 50 pounds of additional sand was added to the new tank to create the current sand bed. Sump has 2 to 3" DSB--Black sugar sand.

Fish--Two Hippo Tangs (the Germans do it, as reported in TFH), common clown, two pink lined wrasse, horselip blenny, blue neon goby, mated pair of bristle tail filefish--all in display. Sump has two female black cap basslets.

Inverts--Assorted snails and hermits all in pretty modest numbers, hordes of bristle worms, 3 clams (two maxima and one dersa), hammerhead coral, alveopora coral, ricordea mushrooms, Briareum sp (starburst polyp), scrolling tubinaria, hydnophora, montipora, Sansibia sp. (blue waving hand), zoanthus polyps, Acropora secale, several unidentified corals from Florida aquacultured Live Rock, many volunteer feather dusters from 1/4 to 3 inches, several species of pistol shrimp, pep shrimp, camel shrimp, etc

Live Rock--Display has modest (50#?) amount, mostly "home made" from concrete mix, sump is 1/2 or more full of softball size chunks of aquacultered from FL.

Feeding--Fish are fed flake and chopped clams, shrimp and silversides about 8 to 10 times per week. Tank is feed various filter feeding mixes 2 to 3 times per week.

Water changes--30 gallons every 6 to 8 weeks.

Problems--Fair amount of nuisance algae (many species) and cynobacteria. Not on corals, but on display live rock, glass, and especially in top 1/3 of overflow

Sea grasses--Late march, 2009, I planted shoal, turtle and manatee grass in the "deep" 1/3 of the sand bed. The turtle and manatee died back. Turtle hasn't been seen since. Manatee may be coming back, but is hard to tell from the shoal grass which had some initial die back, but now is spreading and fairly vigorous. Towards front of tank the shoal grass is about 4-5 inches tall and pale green, towards back of tank it is 6-7 inches tall and very dark green. I am not sure what makes the difference, especially since the healthiest looking grass gets the least light.

Fertilization--After much reading, I decided I should add both KNO3 and Iron. (I also add Calcium and Alk on a daily basis.)

KNO3--I purchased some Dexol Stump Remover from my local Menards. According to the MTSDS it is 100% KNO3 by weight, which is of course not the same as being "lab grade" KNO3. I added 1/4 cup to 1 Liter of RO water (didn't have any distilled on hand) and it created a crystal clear solution with only two or three specks of black impurities visible to the naked eye.

Nitrates were not detectable (Salifert) prior to starting to fertilize. I have been adding 20 ml of the KNO3 solution each day, which raises the Nitrates to between 2 and 5ppm shortly after addition. They have been at or near zero 24 hours later when I retest and re-fertilize. Today I was home and they were very near zero about 7 hours after addition, so I added another 20ml of KNO3 solution.

Iron--it is very hard to determine how much to add to the tank. I have a 10% chelated iron solution that was sold to me by Gulf Coast Ecosystems, which also sold me the sea grasses. Russ at GCE advises shooting for iron in the range of 0.1 to 0.5ppm for sea grass only systems. He advises slow additions, but isn't aware of any real reason why this should be a problem in a mixed reef/seagrass system either. Sarah (on this forum) is much more cautious and advises going no higher than 0.05ppm. Everyone agrees that iron is very hard to measure and Randy's excellent articles in the Advanced Aquariust make it clear that what you really need to know anyway is bioavailable iron, which may not be the same as total iron as measured by most kits. Hmmm. Hmmmm. Hmmm. What to do? So far I have been pretty cautious and have been adding only ONE drop per day of the 10% iron solution I have. (I believe that is still about the same as 40 drops per day of the solutions that Sarah was using--which is about what she would add to a 50 gallon system, IF I understand her posts, which is a big "IF".)

Anyway, I sprang for the $100 it costs to get a LaMotte Iron testing kit shipped to me, which is apparently about the best kit the average hobbyist could afford. Once it arrives I plan to measure my "baseline" iron amount both in my salt water right after mixing and in my display tank now that I have been adding a single drop per day. Unless someone can give me better advice, I plan to slowly raise the total iron in my tank to something about 0.1ppm higher than whatever the baseline is, unless the baseline is substantially above "not detectable", in which case I will puzzle over it a bit more.

And the results? Well, to be honest, I really can't tell if my modest KNO3 additions and miniscule Iron additions have made any difference at all so far. The grass under the brightest light still is a little pale compared to the grass at the rear of the tank. The grass is still growing and spreading shoots, but I couldn't say if the rate has changed at all. Everything I want to have in the tank still seems healthy and happy. So do the various nuisance algae and cynobacteria.

I will be sure to post an update if anything particularly good or bad happens. I hope that I am slowly changing things for the better and that someday my sea grasses will be even more lush and full and the nuisances will be nearly gone or greatly suppressed and all the fish and corals will continue to be "happy as the clams". As long as nothing goes in a bad direction really fast, we are probably doing alright.

Cheers--

 

[monicaswizzle]

Here is a Picture

Here is a Picture

 

[3D-Reef]

Hey Monica!Nice stand of grass You got there!

I'm not exactly sure why there's a diffference between the front and back.Shoal grass is one of the starter grasses,it is usually is established first,then turtlegrass comes in and eventually takes over as the sand matures/becomes nutrient ladden.

Just thinking out loud:One possibility the grass in the back looks better,is because it's not growing at such a fast pace that it's not using up the nutrients around the roots,like in the front.In other words,the front part is using up all the nutrients as fast as it can because of the intence lighting.Is there a difference between the "thickness" of the grass,front-back?

While Sarah had good luck in dosing nutrients to the water column,I on the other hand,like You,experienced HA and cyano blooms when dosing in that mannor.So keep a sharp eye out for the HA and cyano,making sure Your not just feeding their growth making things worse while dosing.

I've read where turtle grass only uses 7%,of it's total needs,from the water column,that means 93% is taken up from the substrate.So based upon that idea I have been experimenting with substrates and what might work there.

I started by useing plant tabs pushed into the bed next to the roots.But,since the sand bed was already mature,this just caused the HA & cyano to go nuts for a few months and I didn't see any change in the growth of the grass.This method may work for a brand new system/sand,but it didn't work out for Me.

Next I tried injecting Fe into the sand.While I did see a spurt in growth for a few weeks,I think the method I used was flawd.I took a syringe and pushed it into the sand,then dosed the Fe.But when I removed the syringe I think the Fe followed it back out into the water column.The results were good,even though the method may have been wrong.A better way may be to use some tubing on the end of the syringe so as not to make a big hole in the substrate(?).

The last thing I've done is to remove parts of the sandbed and replace it with some laterite followed by new sand on top.The results have been that I haven't dose any Fe and the grass where I have the laterite,are growing in green and lush.The other side of the tank is still putting up shoots,but there aren't as many leafs and the ones that it has are yellow at the ends.

IMO I would discontinue the KN03 additions because this may worsen the cyano & HA and try the injecting Fe into the substrate.If You feel that the grass is N or P limited,You could try pushing in 2-3(at most) shrimp pellets next too the roots,and see what happens.

Let us know how the Fe test kit works.I'd be real intrested too find out.

 

[monicaswizzle]

Hi 3-D--thanks for the comments.

I am still puzzling over why the grass towards the rear of the tank seems "healthier" than the grass in the main part of the tank where it gets more light. Your theory that the main part of the tank may be growing faster and therefore using up more nutrients is an interesting one. I am not sure it is what is actually going on, but it is interesting to think about.

For what it is worth--

The grass in the "rear" of the tank is about 2 to 3 inches taller than the grass in the main part of the tank (I think I understand that now--see below). The grass in the rear is also noticeably darker green, although at least some of that might be because it is under less intense light and so "appears" less washed out to the eye. Now that you ask, it also seems that the grass in the rear is growing a little "thicker", meaning that there is less space between the blades and less unoccupied sand. That is the least certain of the differences and could still be an artifact of the way I planted it. I didn't especially try to make that area more densely planted, but the activity of planing raised such a thick cloud of gray particulate matter that I couldn't really see what I was doing, so who knows.

Anyway, about the height difference. Today I spent 15 or 20 minutes just "looking around the tank". (That is why I have them after all--too bad life is so busy that it is a rare thing for me to actually do.) While I was sitting there I noticed that my 7" long Hippo Tang (Pacific Blue or Paracanthurus hepatus) would swim over the grass bed, reach down and nip the end off of a blade of grass. Most of the time she was only nipping off a quarter inch or less from the blade tip, but several of the nips took a good half inch if not more. I suspect it is a little harder for the tang to maneuver right against the rear wall of the tank, so that may explain why the grass there is longer! I don't think that is the whole explanation though, because by that reasoning, the grass near the front wall should be equally hard to get at and it should be longer also. It isn't, or at least not nearly as long as the grass in the rear. Also, the grass in the front of the tank definately has considerably more yellow (even taking into account the "wash out" effect mentioned above), so there is something besides herbivory going on--unless the nipping of the grass would also cause it to yellow somewhat?

Speaking of herbivory--not only does my large hippo tang like to nip the grass blades (so far I haven't seen the 3" hippo do any nipping), but so does my red-lipped/horse face blenny. Lucky for me the growth rate seems to be higher than the rate of consumption--those fish have been in the tank since before I planted it, so they must not be eating it faster than it can grow. It actually is good, because ever since I added the extra 400 watts for the grass, the fresh seaweed I add for them to eat blanches out within an hour or two and turns to soft mush that they won't touch.

Interesting ideas about trying to get the iron into the sand, not in the water column. I have some science grade glass pippettes that might make it possible to inject the iron solution fairly deeply in a small hole. I am still not sure that it wouldn't mostly follow the pipette back out. Once I get my iron test kit I might do some experiments seeing if adding iron to the water column actually raises the iron level faster than trying to add it to the DSB does.

Fun to fool with. Just glad that so far nothing seems harmed by my attempts to fertilize. (The cyno and mirco algaes were definitely problems before I added the grass. KNO3 doesn't seem to have made them worse, but I can't say that the grass is outcompeting them either.)

Cheers--

 

[3D-Reef]

It could also be the obvious,too much light.You could try an experiment by shading part of the grass on one end for a couple weeks to see what happens.

Hehehe those pesky tangs!I put a little shaol grass in My DT and My Sohal tang devoured it in short order.As long as the grass is out growing the nipping,I wouldn't worry about it.

Oops! I'm late for work.Gotta go.

 

[lancer99]

Interesting stuff!

I started my "experimental" 29G seagrass tank, with a 150 watt pendant, 20 months ago, with 6-7" of sugar sand and a gallon of Miracle Mud mixed into the bottom layers.

Shoal grass and manatee grass both did well for a while (~6 months), but both eventually died off. Turtle grass looked horrible at first, but is still with me...but only a few stems at a time, with 3 or four leaves.

-R

 

[monicaswizzle]

Well, thanks for the comments. Here is a brief update:

If I add about 20ml of KNO3 solution each morning my Nitrates rise to between 2 and 5ppm (even the Salifert test kit is pretty hard to read with precision) and are back well below 1ppm by the next morning, so I am using that as my Nitrate dose for now.

I just received the LaMotte Iron test kit from FedEx, am anxious to see if it is measurable in the tank and decide what to do with Iron. For now I have been adding just one drop of a solution of 10% chelated iron to the tank each day (total capacity is 150 gallons, of which I estimate 100 gallons is water).

The grass looks about the same as it did before I started this regimen. The part in front is definitely more yellow and shorter than the part in the back. Definitely growing, but not so rapidly as to make me sit back in amazement.

I have noticed a slight reduction of growth in the nuisance algae, especially in my overflow where it tends to get a lot of light and grow pretty rapidly (it is protected from the tangs and blenny and file fish there, so it has no herbivory to keep it in check). I "harvested" the algae in the overflow early last week and although it certainly has grown back, it is noticeable that it is growing back more slowly. I assume this is because the grass is doing a better job of competing for phosphorus since it has a steady supply of nitrogen at this point in time. All speculation, but a nice thing to see.

The cyno seems about as "healthy" as ever. It is remaining confined to the open spaces on my live rock and, to tell the truth, I don't mind how it looks, so as long as it doesn't spread I won't worry about it too much.

The corals and clams seem to be as "happy" as ever with one sad exception. My blue waving hand coral appeared a bit closed up on Thursday, so I suspended my fertilization for the day on the assumption it might be nitrate (or less likely iron) stress. When I got home Thursday night the coral was simply gone. Only one small polyp remained on the main colony and the three or four polyps that had started to spring up at new locations around the tank are also gone. I am sure this is the work of those nasty little file fish (a very recent addition to the display tank). After several days of good behavior they must have had a hunger attack and finished off a patch of waving hand with about a 3-inch radius in one day! This is similar to how they behaved with the calupera in my QT tank. The first few days they left it alone and the next day it was all gone except for a few roots. I may come to regret the day I ever added them to my collection--though they are damned "cute" and it is great to see them swim among the sea grass as if they are really at home. I just hope they don't do in the hammer head coral next.

I removed the last bit of the waving hand to the "sump" tank where it won't be eaten, but it won't get enough light either. Later today I will add more light to my QT tank and try to move it there for recovery. It can probably continue to live there unless I find another solution. I will have to move it from there if I ever house a fish that needs to be treated with copper.

Anyway, the fertilization is going fine as near as I can tell. I suppose I could try reducing the light for a bit and see if that could actually be helpful to the grass. From what I have read it is pretty hard to give them too much light and since the tank is a 90g and the light is about a foot above the water I wouldn't think it is too much, but it is true the grass is looking better in the "dimness" of the rear.

Can't complain. Having fun.

 

[monicaswizzle]

Testing For Iron and Adding Some

Testing For Iron and Adding Some

Well, my iron test kit (LaMotte) arrived during the week and today I had a chance to test for iron. Here are the results:

1) Well water that I use for replacement water and to mix up my salt water--not detectable.

2) Mixed up salt water that has been sitting for about a week--some iron, but less than the lowest measure (0.05ppm) on the test kit. (I use Proline Super Salt, FYI)

3) Display tank (last water change was about 1 week ago, I have been adding ONE drop of 10% iron chelate every day for about 2 weeks)--not detectable.

The fact that there is more iron evident in my salt mix than I can measure in the display tank, despite daily additions of iron, leads me to believe something in the tank is using the iron and/or binding with it to take it out of the water column.

So, according to the directions supplied by Russ at Gulf Ecosystems, 1ml of the 10% iron solution would raise the iron level in 10 gallons by 0.2ppm. I estimate that I have 100 gallons of water in my system, so I added 2.5ml (36 drops) in the belief that should raise the total amount of iron to 0.05ppm, which is the lowest amount the test kit can measure. I will test the iron in an hour or so, after it has had plenty of time to mix in with the tank water, but not a lot of time to be taken out of the system. Assuming I am near 0.05ppm, I will closely observe the inhabitants and measure the iron again tomorrow.

 

[HighlandReefer]

Great thread.

Following along.

 

[rando45]

very informative!

 

[monicaswizzle]

Thanks guys. There are so many variables from tank to tank and situation to situation, it is pretty hard to imagine what will actually be useful, or at least of interest to others.

About an hour after I added Iron yesterday the test showed that there was definitely some in my system, but still less than the 0.05ppm which is the bottom range of the test kit. Unless I notice signs of stress on some of the organisms, my intention is to shoot for something around 0.08ppm and then hold it there, so this morning I boldly added another 2.5ml of iron without testing to see if the total amount had dropped back to undetectable levels or not. So far all of my organisms seem to be happy as ever, so I am not too worried about short term iron toxicity. Tomorrow morning I will test for iron and only add it if the level is lower than 0.08ppm.

Thanks for the interest. I will try to update if anything dramatic happens.

 

[monicaswizzle]

Well, 24 hours or so after adding 2.5ml of the iron solution, iron was back to not detectable with my kit. So, I will add another 2.5ml today and see what it is like tomorrow morning.

 

[monicaswizzle]

Iron still drops to undetectable within 24 hours of every addition, so something in the system is certainly using/absorbing the iron. I still don't observe any adverse effects on any of the tank residents, and it does appear that the seagrass is a bit greener than it had been. I decided to up the dose of iron to 40 drops per day--about 3.13ml of 10% chelated iron solution. So, current daily dose for my system (140 gallons total capacity of which 100 gallons or so are water):

3.13 ml of 10% iron solution
15ml of KNO3 solution (raises NO3 to about 2-5ppm, drops down below 0.5ppm in 24 hours)

 

[HighlandReefer]

Iron will get tied up in the dissolved organic matter in your water column and may possibly be exported by a skimmer (certainly not all will be exported). Iron can become attracted and attach to your rock and sand. Iron can precipitate out as iron oxide. Your test kit will not detect these forms of iron.

Dr. Randy Holmes-Farley goes into more details in these articles:

First Iron Article: Macroalgae and Dosing Recommendations
http://www.advancedaquarist.com/issues/aug2002/chem.htm

Second Iron Article: Iron: A Look at Organisms Other than Macroalgae
http://www.advancedaquarist.com/issues/oct2002/chem.htm

 

[monicaswizzle]

Thanks Cliff

I don't use a skimmer, so that source of export isn't an issue in my system.

As I understand it (not all that well, to be honest), the fact that I am adding chelated (sp?) iron makes precipitation somewhat less likely. I am not altogether clear on whether or not that has any impact on bonding with rock and sand or not.

Anyway, it is certainly true that there are lots of possible places for the iron to go that don't include use by the plants I am intending to fertilize. No one seems to have definitive answers as to how toxic/undesirable it may be to add iron to some of those possible places.

All of which makes for exciting times when trying to decide if it makes sense to dose iron or not.

 

[HighlandReefer]

Beyond the Refugium: Seagrass Aquaria by Sarah Lardizabal
http://reefkeeping.com/issues/2006-04/sl/index.php

This is what Sarah recommends regarding dosing iron:

"Iron, already embraced by some reefkeepers with very large refugia, is also beneficial to seagrass culture. Unfortunately, at this writing it is still unclear which iron sources are best and at what dosing levels they are safe. Dosing according to manufacturer instructions using any of the commonly available chelated preparations seems to be sufficient. Until bioassays are conducted to verify the safety of iron dosing, a more complete recommendation cannot be made. Those with a keen interest in this area and the advantages of using iron EDTA over iron citrate or gluconated iron preparations are advised to read Holmes-Farley's article on iron dosing.25"

 

[monicaswizzle]

Another Update

Another Update

Well, here is the current status:

Nitrate Dosing:

Each morning I add 10ml of KNO3 solution to the tank. That seems to immediately raise the NO3 to somewhere between 5 and 10ppm. By the next morning it is still detectable, but is clearly below 1ppm. I am not sure if that indicates the plants are getting all the NO3 they need, or if there is some reason they have a hard time using the last bit of NO3. (Prior to dosing my tank always ran with NO3 not detectable, so I assume it is probably a sign that I am dosing plenty of NO3 for the current need.) I plan to continue on this program and monitor closely for NO3 build up, in which case I will skip a few days and/or reduce the dose. On the other hand, if the tank starts returning to undetectable levels, I will assume that means growth is causing a greater NO3 need and up the dose a bit. (All this assumes I don't observe "undesirable" effects of the dosing.)

Iron Dosing:

This one is more of a challenge to determine. I am currently adding 50 drops of the 10% solution--a much higher dose than Sarah recommends. Shortly after dosing this raises the iron to a detectable level on my scale, but still below the lowest reading, which is 0.05ppm. By the next morning the reading is always undetectable on the scale. I have no idea what this means or how to interpret it. According to Russ at Gulf Coast Ecosystems, where I bought the sea grass and the iron, in a sea grass only system I would want to up the dose dramatically until the tank was running between 0.1 and 0.5 ppm on a regular basis. This is way more iron than Sarah would seem to recommend under any circumstances, certainly in a "mixed reef/lagoon system" like mine is. Who knows if the sea grasses are using any/all/most of the iron, or if it is binding with things in the sand bed and/or live rock, or precipitating out of the system. Since Russ seems to report actually running iron at much higher levels, in tanks with deep sand, I would assume that it isn't all ending up bound in the sand bed or precipitated out, but there may be major differences between his system and mine.

Is all of this "helping" the grass in any way? Hard for me to say. The grass in the back of the tank remains much taller and a bit greener than the grass in the front (maybe I should try shading the front a bit to determine if I actually could have too much light). Some of the grass in the "mid" area is clearly much taller than it was before--could be due to dosing, or it could just be growth I would have achieved anyway. Overall color of much of the grass is still a little yellow IMO, but not as dramatically so as before I began to dose (this is really hard to "measure" without a good benchmark--it may not have changed at all, very hard to tell). Most of the grass in the mid to front of the tank is still considerably shorter than the rear of the tank, but that is less uniformly true. Maybe the grass is now growing enough faster than the herbivores can eat it that even the "easy" to eat grass is getting taller? The grass is definitely taller and thicker (more blades) and covers more of the tank than when I started dosing. It was spreading anyway before I began the dosing, so not sure what the cause is--dosing or time or both. I don't see any bad effects on the grass, that is definite.

The rest of the tank? I haven't seen any dramatic bad or good effects. I still have a fair crop of nuisance algae. My impression is that they are growing a bit less rapidly, but the change is subtle if at all. Cyno is still on much of the empty rockwork. Maybe not as "thick", but that is a marginal difference at best. No corals seem to be suffering. Clams and corals all continue to grow at pretty decent rates.

One dramatic change of late is an explosion of the tiny (Astrae?) starfish in the tank. I have no idea if that is dosing related or has some other cause, but yesterday I counted 37 of them clinging to the front pane of the 90 g display tank alone. There were dozens more in the sea grass and on the liverock. I am not sure why they have recently increased from what used to be an occasional sighting. I assume they will likely "crash" soon and go back to more normal density.

That's all for now. I am toying with bumping the iron dosing up even more, but not sure it is justified, since I am getting good growth on the grass anyway.

 

[Samala]

You are doing something very important with this aquarium: being willing to experiment!! I'm stoked to see someone facing the iron situation head on.

I've honestly always erred towards caution when writing about iron because so many aquarists keep their displays in a mixed lagoon style if they have marine plants at all. Many house pretty sensitive fish species in addition to all the corals. I simply don't. I've almost always kept fish that were invariably hardy and don't dally around a lot with coral. I take too many vacations and spend too many nights away from home.

In my current shoal/manatee system (40gal breeder) I dose to 0.2ppm Fe, and do so in bursts. As in, drop it all in at once, go about my day, see it later on in the week and redose to that desired level.

I started to see issues with cyano and on occasion diatoms when I was dosing KNO3 to 10ppm for nitrates in bursts. I switched to a drip system that slowly delivers NO3 to the tank, but does so throughout the day. Basically like an IV drip. This has worked out very very well so far.

Are you pH and alk levels stable throughout the day? I have fought this problem in all my systems so far and cant seem to overcome the use of carbon in the system on a long term basis even with heavy aeration and supplemented CO2. Its a puzzle. One I look forward to solving.

Cheers on your courage and your hard work so far. Its a beautiful aquarium.

>Sarah

 

[HighlandReefer]

Sounds to me like shading the areas where the grass is not growing as well with perhaps a screen may improve the growth in those areas. Definitely worth a try IMHO. Perhaps just shade half that area as an experiment.

Too much iron can lead to phytoplankton blooms according to reasearch I have read. I would keep a close watch for this, while dosing iron. I was hoping some of the seagrass experienced hobbyists would chime in.

Bluenassarius is one of the hobbyists who is experienced in the marine plants. He spends much of his time on http://www.marineplantedtanks.com

 

[HighlandReefer]

Sarah,

Great to see you chime in.

Have you tried using the Ferrous Gluconate for dosing?