Diatomes even though chemistry tests good.

[jimmaki]

I'm at my wits end, maybe someone can help me understand this problem and suggest a possible solution.

I am experiencing a diatom outbreak in a well established tank, and nitrates and phosphates are undetectable. Silicates are also zero according to a brand new test kit. Two separate LFS's also confirm those readings.

I have done four 30% water changes. In the last two water changes I siphoned out half the sand bed each time. The tank is now bare bottom. It's a 100 gal reef with 150 lbs of seasoned/cycled Fiji live rock that's been in there over 10 years. One hour after doing the last water change I had a brownish cast on the bare bottom. By the end of the day there was a thin brown film on the the front, sides and back as well.

Most all the corals have either shut down or died. A few snails are still alive as I can see their tracks as they eat through the diatomes growing on the back wall. Before each water change I cleaned all the glass and turkey basted all the live rock and let everything settle on the bottom and siphoned it out.

There are only six fish in the tank, a yellow tang, a hippo tang, two perculas and two chromis. The tank has a built in wet/dry and a custom skimmer. I'm running a poly filter and Chemipure Elite.

I also just got some silicate remover but I'm hesitant to use it since the same company (Sera) also sent a test kit with it and my RO/DI, makeup and tank water all read zero silicates. I'm using a Red Sea phosphate test kit and a LaMotte nitrate kit ... both read zero. I use a 6 stage Spectrapure RO/DI unit with two silica buster final filters and the output tests zero TDS.

I'm at the end of my rope and don't know what to do next. I would wait for the diatomes to exhaust the silicate supply but the diatomes are covering the rocks and corals and smuthering them. Help! Please!!

 

[Steve Wright2]

very frustrating Jimmaki

have you tested ammonia and nitrite? you may have removed a percentage of your biological filter when you removed the sand bed , and that may also account for coral losses

also was that sand bed in for 10 years before you decided to remove it?
as it may be released Hydrogen Sulfide affecting the corals?

http://reefkeeping.com/issues/2005-12/rhf/index.php

did you add anything new in terms of pumps or plastic or anything, as they can also be the source of bio available silicates , I believe

The test kit may well read zero silicates in your aquarium, simply because the diatoms are utilising them ( same principle as Algae and the 0 nitrate test kits)

Not sure really what to advise as I have always been of the opinion that they need to run their course and once silicates are used up they will fade away

boosting the CUC may be something to consider if the problem persists

the polyfilter was a good idea, as that will deal with excessive biological waste, if your corals are suffering as a result of a small cycle issue related to removal of sand bed

sorry I do not have any definitive solutions
I do hope that someone else does have

Steve

 

[jimmaki]

Yes, ammonia and nitrite are zero.

Only recently added plastic are two more Koralia pumps which I added to increase flow over the bottom in an attempt to keep the then existing sand from turning brown. The sand was loaded with pods, baby bristle worms and cerinth and astrea snails. All but a handful of snails got siphoned out with the sand. (sigh) I'm desperate to get rid of this problem! I will add grunge back once I get things under control.

The sand bed was not deep, only about a inch in front and 2" in the back. It was loaded with ditritus but I siphoned it out taking sand and ditritus together so very little escaped into the water column. There were some black pockets. I don't think the sand bed was doing much denitrification to speak of since I didn't see a rise in nitrates after I removed it. I think there's enough live rock to keep up with things since there are only six fish and I feed lightly since the tangs eat off the reef and the chromis are happy with residual plankton left over from feeding corals. There is no other visible micro algae, cyano, hair, bubble, green or other excess nutrient signals in the tank other than the diatoms.

I can boost the CUC but it doesn't get rid of the source of the problem which I have yet to identify. I've been using Instant Ocean Reef Crystals for many years. Maybe something in their formula changed? I dunno. I test the mix for silicates, nitrates, phosphates, alk, temp, pH, ca, mag before slowly adding it into the tank. Maybe I'll try some Red Sea Coral Pro and see if that helps.

I'm about at wits end. The water going in for water changes test zero nutrients and there's no diatoms in it utilizing them that I can see, so I think if I keep changing water eventually I'll get whatever the diatomes are utilizing down to an unsustainable level. I've even toyed with the idea of a 100% water change. Unfortunately, I can't get all nutrients out of the rock without killing my biological filter, and I sure don't want to do that. So my current plan barring any bright ideas popping up ... is to continue water changes until I dilute the problem down to non-supportable levels.

 

[bertoni]

I suspect the bloom is cyanobacteria or dinoflagellates. I would stop the water changes, which can fuel microbial blooms, and slowly ramp up the GFO level in the tank. Even if the bloom is diatoms, they require phosphorus, too.

 

[Nano sapiens]

^^

In my experience, a bloom of the type you are describing is brought about when an old, detritus clogged sand bed is disturbed. I had the same issue, but elected to keep my sand bed, so I did a lot of vacuuming

The bloom took a few weeks to subside after it had run out of whatever fuel(s) it was using. Measuring parameters is interesting, but I found that Phos and Nitrate always tested '0' during the outbreak because they were being consumed rapidly.

 

[Steve Wright2]

I suspect the bloom is cyanobacteria or dinoflagellates. I would stop the water changes, which can fuel microbial blooms, and slowly ramp up the GFO level in the tank. Even if the bloom is diatoms, they require phosphorus, too.

This got me thinking

Jimmaki did you recently change salt brands or have you continued using the same salt for a while now?

 

[philosophile]

sandbeds do a lot of filtering... Its probably pound for pound the best filter you have in your tank. Surface area= bacteria=filtering.

Anyways... Have you checked your RO/DI filters? maybe its time to change the filters. Silicates usually don't stick around in the tank for a long time. It usually gets skimmed out, or used by diatoms... which gets skimmed out... What kind of CuC do you have? snails and some fish really love chowing down on diatoms.

 

[jimmaki]

After I removed the entire DSB, I was still getting a lot of tomes on the live rock. I figured nutrients were leaching out of the rock so I blasted them with a baster. After several rounds of blasting and water changes, I finally took the aquascape apart, took the rock out and cleaned it really well in a bucket full of tank water. That did the trick. No more diatomes.

 

[jimmaki]

No, I've always used IO or RC.

 

[jimmaki]

RO/DI filters were changed about six months ago.

I removed the DSB and have been running BB for about a month. Amazing the amount of detritus that accumulates on the bottom despite a lot of Korallia movement throughout the tank. I am starting to get algae (green and coraline) growing on the bottom and I don't like the look. I think I'll put in a SSB about 1-2"

Any tips on putting sand into a running/existing reef? My though was to use a funnel on top of a piece of PVC tubing. Hopefully it won't cloud up the water too much ... my concern is a lot of sand "dust" settling on and hurting the corals.

 

[Mekanic]

I had diatom issues, changed salt and added a booster pump to increase membrane rejection (on a well so I was only at 40psi) has went away almost completely


FWIW, I was using RC... Switched to Red Sea and diatoms went away.

 

[coralsnaked]

Sounds like a-typical OTS Old Tank Syndrom brought on by the process of removing the deep sandbed which was 10 years old. There is a process for that which will prevent your recycle and consequently algae blooms,m just like w/ a new tank. It will pass but the results on established corals will be unknown until the storm passes. I currently have one sandbed tank left to tackle. It is a deep 8" sandsifting bed which is 8 years old. Since the tank is so large it is going to be a bit of a beast to manage thru the process so I have decided to farm out all critters and corals. Not really interested in softies too much anymore, although the old girl is a pretty one. Tank has some ancient deep water Tonga base rock, which I will utilize after recuring.

Merry Skerry

 

[bertoni]

The funnel approach should be safe enough for an inch or two of sand. I'd remove any algae buildup before adding the sand.

 

[jimmaki]

I had diatom issues, changed salt and added a booster pump to increase membrane rejection (on a well so I was only at 40psi) has went away almost completely


FWIW, I was using RC... Switched to Red Sea and diatoms went away.

Really! Wow, I didn't think there was that kind of difference between top name commercial salts ... think there are phoshates or diatoms in RC or do you attribute the booster pump to purer RO/DI water? I'm at 60psi on city water after a RainSoft water softener.

I was using Instant Ocean and the diatoms went away after several hundred gallons worth of water changes on a 100 gal tank. The last time I went for salt the LFS was out of IO so I bought a bucket of RC. The first water change using RC was a week ago and I haven't seen any diatoms, but I have seen an increase an faster reappearance of that light white dusting of algae and some darker brown algae that grows on the glass.

 

[jimmaki]

Thanks for the good suggestion, I will do that! (remove algae buildup on the bottom glass first) I'll let you know how the funnel works.