one I would get rid of the fluval system ( hold onto it and use it for running something like carbon or phosban or such when needed just throw the chemical in a mesh bag and run it when needed), they are a known problem in saltwater tanks, they are mainly for a freshwater setup and will lead to nitrate issues if not cleaned regularly.. I would also not use the flakes for food they are known for phosphate trouble, change over to a quality frozen food... There are 2 bulbs in the fixture? it may not be enough light for the corals you have in the tank. If t5 you are probably going to need a 4 bulb fixture but would need more details on what lighting it actually is..