I need to decide

[king kong]

I am almost there thanks to all your help. 50 gallon medium to high light plants, fixture hung 30" above substrate. The TEK looks great, have a supplier near buy, 48" but......2 tubes or 4 tubes. The guy inthe store says I will not need 4 tubes. What would you do?
Thanks,
Gary

[Trickerie]

At 30" each bulb will give you roughly 20 PAR the substrate. So, for medium to high light you will need 4. Bring the fixture to 25" and you would only need 2 and get the same amount. Reference:

[Complexity]

I have 4x54w TEK fixtures for my 75g and 90g tanks. You can grow plants just fine with 2 bulbs, but since you're going to be hanging the fixture 30" above the substrate, I'd get the 4 bulb fixture. It will give you more flexibility.

If you just want lower lighting, you can always choose to run just 2 bulbs. But if you want to grow higher light plants with EI ferts and injected CO2, you can run all 4 bulbs.

[OVT]

Or better yet, get a 6-light fixture. The difference in price is not that great.
That's what I run over my 4" 65g