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DaveK · 03-18-2007, 05:38 PM

The main thing you got to do is you have to get at the underlying source of the problem.

I suspect you have several possible problem areas you want to check out.

First, check your feeding schedule. You may be feeding way too much, or food may be getting into the filtration system and decaying there.

An 800 l tank works out to about 210 us gals.

The skimmer you are using is far too small for the size system you have. You want to be using a skimmer rated about twice the tank size. In other words if the manufacturer says it's good for a 100 gal tank, you don't want to use it on anything much larger than a 50. For your tank, you want a skimmer rated for a 1600l tank (about 450 us gal).

The marble chips on the bottom are likely a source of nitrates, especially if they are course. They tend to become a nitrate factory because they trap dirt. I would remove or replace them. The options are bare bottom, just enough coral sand to cover the bottom, or a 4 inch deep sand bed. In other words, if you use coral sand to form a sandbed it should be deep. Each method has advantages and disadvantages.

To get the nitrates down, you will most likely need to make some massive water changes. Check up on your RO unit and test the newly mixed water, and make sure the nitrate and phosphate reading are 0.

Make sure you keep the mechanical filter clean, and that it comes before anything else in the filtration sequence.

Other things you can consider doing -

Convert the system to a FOWLR (fish only with live rock). You'll need about 220 to 320 lbs (100 to 150 Kg) of live rock, and you will need to cure it in something other than your main tank. Once it's cured you use it in the main tank for decoration and for the biological filter media. Then over a period of weeks, remove the bioballs and sintered glass.

Add a refugium. For a tank you size I'd use about a 50 gal tank. Since you already have a sump, you set up the refugium tank so that water runs from the sump to the refugium and back to the sump. You want to use the clean water in the sump, at the same point as the main return pump. The refugium should be drilled and set up with an overflow.

Now a refugium can do a lot of great stuff, and there are various ways to set one up depending upon what you want it to do. In your case, it is there to consume nitrates and phosphates. So what you want to to is fill it with about a 4 inch deep sand bed, and some macro algaes. For the sandbed I'd use a fine coral sand, about 2mm grain size. For macro algae, Caulerpa is often used, so is Chaetomorphia. You can also add some live sand to seed the sandbed. You'll also need to put some lighting on the refugium for the algae to grow.

What you want to have happen is the refugium to form an anaerobic area in the sand bed. this will fed on nitrate. It's important not to disturb the sandbed below the top half inch or so, once it's established. The other thing that will happen is the macro algae will grow, also consuming nitrate and phosphate. As the algae gets dense, you remove it. If you have tangs or similar fish, you can feed some of it to them, but most of it should get discarded.

That should give you some ideas on things you can do.

03-18-2007, 05:38 PM	#13 (permalink)
DaveK Neon dottyback Join Date: Nov 2003 Location: Philadelpahia, PA Posts: 653 View Gallery Karma Komment	Re: Siporax The main thing you got to do is you have to get at the underlying source of the problem. I suspect you have several possible problem areas you want to check out. First, check your feeding schedule. You may be feeding way too much, or food may be getting into the filtration system and decaying there. An 800 l tank works out to about 210 us gals. The skimmer you are using is far too small for the size system you have. You want to be using a skimmer rated about twice the tank size. In other words if the manufacturer says it's good for a 100 gal tank, you don't want to use it on anything much larger than a 50. For your tank, you want a skimmer rated for a 1600l tank (about 450 us gal). The marble chips on the bottom are likely a source of nitrates, especially if they are course. They tend to become a nitrate factory because they trap dirt. I would remove or replace them. The options are bare bottom, just enough coral sand to cover the bottom, or a 4 inch deep sand bed. In other words, if you use coral sand to form a sandbed it should be deep. Each method has advantages and disadvantages. To get the nitrates down, you will most likely need to make some massive water changes. Check up on your RO unit and test the newly mixed water, and make sure the nitrate and phosphate reading are 0. Make sure you keep the mechanical filter clean, and that it comes before anything else in the filtration sequence. Other things you can consider doing - Convert the system to a FOWLR (fish only with live rock). You'll need about 220 to 320 lbs (100 to 150 Kg) of live rock, and you will need to cure it in something other than your main tank. Once it's cured you use it in the main tank for decoration and for the biological filter media. Then over a period of weeks, remove the bioballs and sintered glass. Add a refugium. For a tank you size I'd use about a 50 gal tank. Since you already have a sump, you set up the refugium tank so that water runs from the sump to the refugium and back to the sump. You want to use the clean water in the sump, at the same point as the main return pump. The refugium should be drilled and set up with an overflow. Now a refugium can do a lot of great stuff, and there are various ways to set one up depending upon what you want it to do. In your case, it is there to consume nitrates and phosphates. So what you want to to is fill it with about a 4 inch deep sand bed, and some macro algaes. For the sandbed I'd use a fine coral sand, about 2mm grain size. For macro algae, Caulerpa is often used, so is Chaetomorphia. You can also add some live sand to seed the sandbed. You'll also need to put some lighting on the refugium for the algae to grow. What you want to have happen is the refugium to form an anaerobic area in the sand bed. this will fed on nitrate. It's important not to disturb the sandbed below the top half inch or so, once it's established. The other thing that will happen is the macro algae will grow, also consuming nitrate and phosphate. As the algae gets dense, you remove it. If you have tangs or similar fish, you can feed some of it to them, but most of it should get discarded. That should give you some ideas on things you can do.