75gal Lighting Queries

[m00se]

Hi, all

I've got a 75gal recently and I've added some live plants (not many, maybe 15 plants). It's not densely planted and I'm injecting CO2 (homebrew, sugar/yeast combo, through my powerhead venturi as detailed in another post). The tank is 24" in depth. The plants are doing OK at the moment with TPN+ supplementation and the current lighting and CO2, but they're not exactly what I would call thriving. My question is about lighting.

I've read that I realistically should have about 1.5-2 wpg, which, taking 2wpg as a good guideline means I should have 150W on my tank. I currently have 3 T8 tubes at 35W each, which puts me barely over 1wpg. I'm going to upgrade to T5s this week, but even with a dual-tube T5 rig with two 54W bulbs in, that would only put me up to 108W. 150 seems like a stretch, unless I just attach the extra T5s on top of my current 3 T8s (!?)

How best should I get up to 2wpg? And surely adding in reflectors etc. would make a big difference? Am I better off going with one of the units that sits on the top of the tank which has inbuilt reflectors, and just lose the lid? Should I add T5s to my current T8s, or just lose the T8s?

Any help would be very gratefully appreciated before I spend any money this week. Thanks!

 

[Dave Spencer]

You don`t need more light. With 3 x T8s, you should be able to grow anything. I only use two out of the three on my 240l.

By increasing the light, you will be asking for algae problems with such a low plant mass.

2WPG is more than enough for any plants, especially on a tank your size, so save yourself some money and stay with what you have. I can`t comment on plant health, but maybe there isn`t enough CO2 or circulation of it, although this may not be the case with such a small plant mass.

Dave.

 

[m00se]

Thanks for your reply. I was starting to think that having 5 bulbs over the tank would be overkill. Evidently wpg isn't everything

The CO2 I'm putting in currently goes through the venturi inlet on my powerhead, which ends up puffing out a squirt of CO2 about once a second. There is another water-output (from a fluval 3+) on the other end of the tank pointing towards that one, resulting in a net downward push right in the middle of the tank. The very small CO2 bubbles coming out end up suspended in my tank for ages (minutes), and circulating over all the plants I have. I don't see any oxygen beading on my plants, but I figure they're getting enough CO2. They had been going a bit brown around the edges for the first week or so, but other posts on here seemed to suggest that was probably some sort of nutritional deficiency such as phosphates rather than a lighting issues. They've definitely greened up a lot now that I'm using the TPN+. I'm probably worrying too much, but I just wanted to be sure that my 1.2(ish) wpg lighting with T8s wasn't the likely source of my plants failing to thrive. I'm probably just being impatient?

Thanks a lot again for your help