quick lite question..

[anov50]

I have a 4 bulb 48" t5 HO fixture over a standard 75gal ( 48"x18"x21"). Atm i have the fixture 6" above the water line (about 25" above the substrate). I dont have a way to measure PAR atm but im wondering if anyone can give me a rough idea how high to suspend the fixture to get the ideal light level (50 micromuls i think) at the substrate?

 

[dutchy]

Based on measurements with my tank, also with 4 rows of T5, gives me 90 micromols at 20 inch above the substrate. PAR drops off @ 10 micromols every 4 inch. So to get at 50 you would need a distance of @ 36 inch above the substrate.

You could also try to just use two bulbs and keep them 4 inch from the water surface, which will give you a nice energy saving.

 

[pepetj]

It's hard to tell without measuring... different lamps provide different readings; I get different readings between the moment after a huge water change and the moment before the next water change also. Water turbidity interferes with light a good deal; quality of reflectors also makes a noticeable difference.

I would move from less to more slowly while observing plant growth and overall tank conditions. Less light makes it easier to manage than more light.

Pepetj
Santo Domingo