75 gallon lighting question

[Zimmanski]

So I just upgraded from a 55g to a 75g and I live my tank now but I reused the lighting from my 55g. It's a aqueon dual normal output t5 fixture and it grows all of my plants extremely well, I have compacta, hydrot. hotto, cabomba green and cabomba furctata. My issue is now that my tank is so much wider the two bulb fixture kinda leaves some shaded areas. I'm not doing co2 so I know a 4 bulb t5ho would grow too much algae so the options I see so far is to either upgrade to a 4xt5ho and reduce the photo period or buy another fixture like I have already and space them out. I've searched and searched but I still can't decide. Anyone have any input or other options for me?

Picture is of the old 55, all the plants made the transfer and placed nearly the same

 

[mohican]

You asked a very good question and I want to follow this post. This is where I feel the old, outdated, WPG rule comes into play perfectly rather than using the PAR rule. To me it sounds like the PAR rule would leave dark spots; I'm not ruling on either. Bulbs and reflectors would probably make a difference though.

 

[Zimmanski]

You asked a very good question and I want to follow this post. This is where I feel the old, outdated, WPG rule comes into play perfectly rather than using the PAR rule. To me it sounds like the PAR rule would leave dark spots; I'm not ruling on either. Bulbs and reflectors would probably make a difference though.

Thank you for responding! I was feeling forgotten about haha

That's my main concern, I'm not looking to go super high light where I would need pressurized co2, I like the light I have and it does amazing with my plants. The problem comes into play when you have a two bulb fixture on a fairly wide tank, my two bulbs do great, for what underneath it. I'm looking to more like spread out my light than increase it, that's why my question is if I should get a 4 bulb HO(cause I can't find a 4 bulb NO) or get the same fixture to add to my current one and spread them out.

 

[Convict2161]

You could get a 4 bulb t5 HO fixture or maybe seeing you can add reflectors to your fixture.

I'm gonna guess your light won't be able to. If you can swing get a nice 4 bulb fixture with a timer. Best of everything. Get 2 daylight 10k and 2 rose bulbs.

 

[Convict2161]

Also I'm far from a plant guy but just trying to help

 

[mohican]

So the question we ask is "at what width do we add another fixture/2 bulbs to achieve our lighting coverage"? Even a PAR reading will be less the farther away from the center. I only run 2 bulb width on my 125 and it too seems to leave dark spots; especially the front and back.

 

[Zimmanski]

So the question we ask is "at what width do we add another fixture/2 bulbs to achieve our lighting coverage"? Even a PAR reading will be less the farther away from the center. I only run 2 bulb width on my 125 and it too seems to leave dark spots; especially the front and back.

Exactly! The par value only measures how bright the light is underneath it, as far as I know anyway. My 75 is beautiful underneath the fixture, it's exactly what I want, but like Mohican said the front and back are dimmer