It is fine to use BUT only if you keep it clean through regular maintanence. If you don't keepit clean it will store up nitrates and pretty much ruin your parameters. lol
I used one on my 55g with a skimmer and was able to maintain 0 nitrates through cleaning it alot and paying attention to the tank.
180g Reef - 60g Rimless Reef -90G FOWLR- 125g Malawi Cichlids- 40b REEF- 34g Fresh Planted-working on- 20L FOWLR- working on
I have a mix of many different saltwater fish amongst my tanks, but I love my Tangs most of all.