hi all, I've got a heavily planted 90 gallon aquarium with four 6" red belly piranha. I'm currently using http://www.thatpetplace.com/pet/prod/209583/product.web. I have a ton of amazon swords, saggitaria, and other tropical plants. Most of the plants are "growing", as in spawning new plants, however they do not seem to be growing upwards. Is this enough lighting for my tank. Dimensions I believe are 48 1/2 x 18 1/2 x 25. I've been looking at other fixtures and they seem to cost a fortune.. I've had the tank for about 6 months now. Any ideas? thanks