Nitrates and Cynobacteria

[Webo84]

I have had a 100 gallon reef tank with a 50 gallon sump and refugium for about 2 years. the main display tank houses LPS, SPS, Soft corals as well as some reef fish. The main readings have generally been good (PH 8.3; Calcium 430 to 440; Alk 11dkh; 0 phosphates). I have an oversized Protein Skimmer (oversized for my tank); a phosphate reactor; and live rock and sand in the refugium. But my nitrate levels have generally been between 5 and 10. I do 18 gallon weekly water changes, but I can't seem to get my nitrates down to 0. I also have increasing build up of Cynobacteria in my refugium. I previously had cyno in the main tank, but I got rid of that about 2 to 3 months ago by skimming out the substrate in the display tank. I don't overfeed my fish.

Any thoughts on how to get nitrates down to 0 and get rid of the red slime algae in the refugium. I was thinking of adding more live rock to the sump and adding calaupa. I have chetomorpha in the refugium, but the red slime is overtaking it and hasn't been doing much to get rid of the nitrates.

 

[Ricko]

What is your fish stocklist?

 

[Itsadeepbluesea]

First what kind of water are you using? Tap water or RO/DI water. If you are using tap water that could be your problem as sometimes tap water can have nitrate in it and by changing the water you are just compounding the problem. As for the red slime algae I would increase your water changes and vacuum the slime algae out as much as you can...and then continue to do that any time you see it re appear. Thats what I did when I had a slime alage problem in a 175 reef. It took a while but in the end I ended up getting rid of it.