I have been following the forums on here for a little while now and decided to enlist you all for some help. I have a 90g Seaclear System II all-in-one aquarium that was moved to my house from another, where it was setup for around 6 or 7 years. The rock, corals and fish all came with it and have all survived and done well for the 3 months the tank has been setup. Filtration wise, the tank has bioballs in the back, phosban in a filtration bag, sea gel in a filtration bag, a poly filter and a strip of 100 micron filter sheet covering half of the drip tray. I have a heater, a chiller and the lights are 4 x 65 watt PCs. Substrate is crushed coral, shallow bed. Fish stock includes 2 yellow tangs, 1 foxface, 1 flame angel, 1 marine beta, 2 clowns, 1 cleaner shrimp, a few snails and crabs. I was feeding twice a day, dry at 1100 and a cube of various frozen foods, thawed of course but not washed, at 1900. The fish ate all of the food within 1 minute when given, but I have cut them back to just the cube of frozen food at 1700 for the last week. And the reason being my nitrates. In the beginning, I had a fish service helping with the maintenance. For the first month, I didn't test anything, they did everything. I had planned to phase them out, so I started testing basic stuff during the second month with those strip tests. Everything looked good except for the nitrates, about 40 based on the color. We told the fish people and they said our nitrates were fine, so I figured my strips were probably junk. I got an API nitrate test kit a couple of weeks ago, as at that point, we planned to get rid of the fish service soon. I tested and the color looked like about 80 on the nitrates. We were doing 10 gallon water changes every 2 weeks but have been doing 10 gallons every 1 week for the last 2 weeks. Nitrates are unchanged so far. The question I have is, what would you guys suggest to lower my nitrates? And I mean other than water changes. What would you guys recommend as a filtration solution to help lower and maintain nitrates at a lower level? Interestingly enough, the corals in the tank have been growing like crazy over the last 2-3 weeks. The mushrooms are freaking taking over and are huge, the start polys are spreading much better now they early on, the xenia is heading for the top of the tank, the leather comes and goes and the torches keep getting bigger and bigger. As well, coralline algae is spreading like wild fire. I actually thought nitrates at these levels would be detrimental to the corals but that doesn't seem to be the case. Anyway, any suggestions would be greatly appreciated. Thanks.