I love the filters. I currently have 2 FX6's and 1 FX'4 on the 210 . They do have good flow, but 210 gallons of water is allot. FLuval FX6 has a pump circulation of 560 gallons and FX 4 has 450 circulation.
Two FX6s AND an FX4 for three fish???
That is absolutely crazy overkill- you should be achieving the EnTiRe nitrogen cycle with all of that. The only water changing going on should be topping off.
That flowerhorn is going to get jacked dealing with all that current