Effective lighting depth

[KErickson978]

At what depth does T5 lighting loose its optimal power? i have two 48 watt t5 fixtures above a 29gal (18in tall) and was hoping someone knows the effective depth for when i decide to upgrade to a 45 tall(24in tall).

[t-bone2]

nope but heres a bump

[KErickson978]

thanks =)