Sand Bed Vacuum Test - Phosphate Liberation?

[LouH]

This is long so I'll cut to the chase for people who don't want to read. Vacuuming 11% of my sand bed had did not result in a measurable increase in phosphate concentration in my tank several hours after doing it. Now, the long version.

I have moved my system several times over the last 5 years, and one thing that was constant each time I moved it was the amount of greenish/black smelly "gunk" that came out of the sand when removed from the tank. I've tried managing my system both by leaving the sand bed alone, and at other times I've siphoned portions of the sand out of the tank at water changes to manage nutrient/detrius buildup. My success with algae management was always good (I still can't get Chaeto to grow), but success with SPS corals was variable. I never did rigorous testing to prove out if one husbandtry technique was better than the other.

My tank has been up for one year now in its current home and I have not touched the sand bed. My water quality seems good with regard to phosphate and nitrate concentrations. Both test as undetectible with Salifert kits. One thing that is interesting is the fact that I had very good SPS growth when I first got my tank reassembled in its current location. When I made the move from California to Nevada, I spent the better part of a week taking the system down, keeping livestock alive during the transit to Nevada with a U-Haul truck, and then reassembling the system. I had very few casualities form the move and all of the old sand and live rock went back into the system.

Fast forward one year and a couple of months and my system is growing montipora, bird's nest and various LPS. Some grow very well but others less so. It varies from colony to colony. I also have a rose anenome which is thriving. However, several colonies of acropora have not thrived. All have lost color, and while some exhibit very slow growth, others have had spurts of growth only to bleach and exhibit tissue necrosis.

This current level of success/failure has led me back to evaluating my system and husbandtry techniques to determine what I can do to improve the health of my acros. I started to consider vacuuming my sand bed again, so I did some searches on RC to see what the experienced folks are doing. It appears as though there are two camps for this:

1. Don't touch it or you will release nitrates, phosphates, sulfates and dissolved organics into the tank which will harm your livestock. There are microfauna/benthic organisms in there doing the work. Leave them alone!

2. Vacuum some of the sand bed with each or some interval along with water changes. This prevents the accumulation of those aformentioned compounds in the sand bed.

Both arguments sound reasonable, but my first hand experience removing sand beds from my system due to moves tends to lean me into the camp that vacuums the sand bed. So, today I decided to siphon out a portion of my tank's sand. My tank has a floor area of 9 ft2. I siphoned out an area of sand equivalent to approximately 1 ft2. The sand depth varied from 3/4" to 2.5", and the particle size is sugar fine. As I uncovered some of the deeper sand, there was the telltale sign of anoxic/anarobic conditions which is blackish sand. The smell coming from the waste bucket had a definite sulfate odor, and the water in the bucket was greenish-black. Unfortunately I could not reach all of the areas of deeper sand so there were shelves of anoxic sand exposed to the tank water.

It took 10 gallons of water to siphon out that square foot, and between buckets I stirred the water to put detrius in suspension and pour it out. I did a final rinse with 5 gallons of tank water and then returned the sand to the tank. I mixed that sand into the surrounding sand and ended up putting detrius into suspension, clouding the tank.

It has been four hours since doing this and the tank water is once again crystal clear. ORP dropped from 330-297 (expected), and is currently at 302. pH remained stable. I just took a sample and measured phosphate concentration, it is still 0, and all corals are exhibiting normal polyp extension and color.

So, it appears from this one event that vacuuming 11% of my sand bed did not increase phosphate levels in my system enough to change the result of my Salifert test kit. I'm going to do this weekly and monitor the response of the acros in my system.

 

[LouH]

Nobody is interested in this? I was hoping to initiate some good conversation on the subject.

 

[vermonter310]

I don't have any first hand knowledge but I am interested as I'm contemplating vacuuming my sand bed..

Have to say though, I am surprised at the lack of response... likely that most have not actually done what you have and spent the time to note the the results...

 

[elegance coral]

I've been vacuuming my sand for about the past 25 years. I did it in my fresh water tanks, and just kept doing it when I went salt. Even vacuumed my UGF.

A couple of years after getting in the hobby, I collected several buckets of sand from the FL. Keys. I used that same sand for over 20 years. The only reason I"m not using it now, is because I moved, my wife hired a guy to clean up the new yard, and I thought he threw away my sand. Ya...I was HOT! Thankfully, I found it in a container behind the shed, so I'll be putting it back in my tank soon.

For me, this is simple. When organic matter rots, it releases nutrients like nitrogen and phosphorus. This is why gardeners use compost piles. Compost piles are not good for our systems because we try to limit these nutrients. If we leave a sand bed untouched, organic matter will accumulate in it. The longer it sits untouched, the more organic matter it will hold. The more organic matter sitting in a sand bed rotting, the more nutrients it will be releasing.

Most of us siphon water out of our tanks when we do water changes. I figure we have a choice. We can just stand there holding the hose, and waiting for the water to drain from the tank, while leaving all the rot and decay on the bottom of the tank, or we can put a gravel vac on the end of the hose, and remove the rot and decay, so it doesn't pollute our water.

I think you're going to have problems trying to vacuum a sand bed with sugar sized particles. Much of the organic matter that's in the sand will be about the size, or larger, than the sand itself. You end up sucking out as much sand as you do poo. With a larger grain size, you don't have this problem. The sand tumbles and falls in the gravel vac, and the poo gets sucked out of the tank.

 

[dlterry85]

i regularly vacuum my sand while doing water changes and have never had a problem. my sand is not very fine, so it sucks up poo and the sand falls back down( a finger over the end of the hose also controls this).

 

[jinks]

I feel like this would pull a lot of the life out of the sandbed. I'm not saying what your doing is wrong just that I wouldn't care to lose all the small living thing crawling around in there

 

[LouH]

The sand particle size is an issue which is why I just siphon it out. Once in the bucket I swirl it around and most of the crud stays in suspension long enough to seperate it from the settled sand.

When I put the sand back I almost immediately saw small worms making new tunnels and small snails climbing to the surface, so they weren't impaired. As far as microfauna is concenred, I can't say, but I wonder how fertile the sand bed is in areas which have turned a greyish black due to decayed matter and low oxygen. For sure those areas are probably too deep for a shallow sand bed, so I'll have to do something about that although regular stirring should prevent this going forward.

 

[KafudaFish]

I feel like this would pull a lot of the life out of the sandbed. I'm not saying what your doing is wrong just that I wouldn't care to lose all the small living thing crawling around in there

The life present there is designed to stay put. Think about the area at low tide where the waves are crashing onto shore. There is much more energy hitting that area than what we could if we siphon our tanks. If you take a sample and look under a scope you would be suprised how much is there.

Sure some life will be lost but you aren't cleaning the entire sandbed each time.

 

[LouH]

Like I stated in my first post in this thread, I got nice growth (and color) in my tank after setting my tank up in its new home. ALL of the sand had been stirred and the crud dumped before being put back into the display. Everything looked very clean, but not sterile. From that observation I could come to the conclusion that the "cleaner" environment in the tank had greater benefit for the inhabitants of the tank than the loss of sandbed fauna that had to occcur during the move and processing of the sand. Keep in mind that I did maintain the sand under conditions similar to the tank's during the move. So, although there had to be some dieoff, there also had to be quite a bit of fauna that survived and was none the worse for wear once back in the display. Another notable observation was that I had no nuisance algae spike after reassembling the system.

It looks like I'm talking myself into continuing down the path of processing my sand bed.

 

[Allmost]

Sugar fine sand, should be packed and not allow any detritus to go under it.

so you can just siphon the top layer. thatès how I do it in my stingray tank.

 

[elegance coral]

You can't keep detritus, and the nutrients released from it, from penetrating a sand bed. Even a fine grain sand bed. Which is why the OP has discoloration and nasty smells below the surface of his/her sand.

 

[elegance coral]

I feel like this would pull a lot of the life out of the sandbed. I'm not saying what your doing is wrong just that I wouldn't care to lose all the small living thing crawling around in there

The importance of this is highly dependent on what you're trying to accomplish in the system. Some of these critters are really cool, and fascinating to watch. Especially with a magnifying glass, or at night. If this is the goal of the system, vacuuming the sand bed may not be appropriate. If the goal of the system is to support delicate coral reef species like acropora, and other stony corals, it becomes very important to limit the amount of rot and decay within the system. Sand beds are capable of holding large quantities of rotting organic matter if they are not cleaned periodically.

It's true that a clean sand bed will support far fewer tiny critters than a dirty one. My goal isn't to create an environment where tiny critters that feed on rot and decay can prosper. My goal is to provide an environment where the delicate creatures, I pay for, can prosper.

 

[EllieSuz]

I vacuum my sand bed during every other water change, but I use a small tube and it vacuums up the dirty water and leaves the sand in place. If some sand begins to rise into the tube, I just put a finger over the end of the hose and allow the sand to settle back down to the bottom. There's really no need to remove sand to clean it.

 

[LouH]

The importance of this is highly dependent on what you're trying to accomplish in the system. Some of these critters are really cool, and fascinating to watch. Especially with a magnifying glass, or at night. If this is the goal of the system, vacuuming the sand bed may not be appropriate. If the goal of the system is to support delicate coral reef species like acropora, and other stony corals, it becomes very important to limit the amount of rot and decay within the system. Sand beds are capable of holding large quantities of rotting organic matter if they are not cleaned periodically.

It's true that a clean sand bed will support far fewer tiny critters than a dirty one. My goal isn't to create an environment where tiny critters that feed on rot and decay can prosper. My goal is to provide an environment where the delicate creatures, I pay for, can prosper.

I would have to say that my goals align with your statements.

 

[Crimson Reefer]

Nobody is interested in this? I was hoping to initiate some good conversation on the subject.

I am very interested in this.

 

[Vinny Kreyling]

Check the phosphate levels in the water from the sand.
Mine was almost double the tank level.

 

[Bretts05jeep]

I am really suprised that there isnt any response form someone who keeps acors that are thriving without vacuuming there sand.

I am just getting into keeping some of the harder sps ( I just have a few monties now ) and trying to set up automated water changes. I was planing on using the return pump to pump the water out of the sump the the basement sink.

So I guess my question is how often does this have to be done for it to be effective.

 

[Vinny Kreyling]

Do some every water change until it's clean enough for you.
Then every so often.
Each tank is different so you will get to know when it has to be done.
Do it on a rotating basis, not all @ once.

 

[LouH]

This weekend was a busy one. No sandbed vacuuming this time. I will resume next week.

 

[elegance coral]

I vacuum all of my sand every time I do a water change. My sand never gets a chance to get filthy, so I don't have to worry about harmful substances being released. Even if there was something bad in the sand, it would get sucked out of the tank, through the gravel vac, and not dispersed throughout the tank. If I had to start on an older tank, where the sand had not been cleaned, I'd do a small section at a time, until it was all clean. Then I would start cleaning larger and larger areas, until I could do all of the sand at each water change, or at least a large portion of the sand.

I don't have a strict schedule for changing my water and cleaning my sand. I shoot for once every two weeks. I have a 300 gallon system. 200 gallon display/120 gallon sump, with no baffles. I change about 100 gallons at a time. I can do this without shutting down the system, or changing the water level in the display. I only remove about 20 gallons of water in the time it takes me to clean the sand. The other 80 I'm just holding the siphon hose or sucking detritus out of holes in the rocks.

I installed the spray bars (pictured below) to keep sand, and detritus from accumulating under/behind the rocks. This leaves just a few rocks near the front of the tank where detritus can accumulate.