Are the bulbs single tube or double tube? How long are the bulbs?
I am guessing they are 40W bulbs. 40W x 6 = 240W / 90G = 2.7 watts per gallon. A reasonable amount of light.
You mentioned CO2 injection and Flourish Excel. Normally people use on eor the other. And Excel gets expensive with a 90G tank.
Assuming proper light and and co2 (or carbon for the excel) the missing ingredient is fertilizer. There is not enough nutrients in tap water for plants assuming good light and co2.
Flourish (Standard, not Excel) or Flourish tabs might be a good choice.
I'll leave the rest for the experts.
I am guessing they are 40W bulbs. 40W x 6 = 240W / 90G = 2.7 watts per gallon. A reasonable amount of light.
You mentioned CO2 injection and Flourish Excel. Normally people use on eor the other. And Excel gets expensive with a 90G tank.
Assuming proper light and and co2 (or carbon for the excel) the missing ingredient is fertilizer. There is not enough nutrients in tap water for plants assuming good light and co2.
Flourish (Standard, not Excel) or Flourish tabs might be a good choice.
I'll leave the rest for the experts.