You could get a custom Catalina Aquarium 2 x 24 inch T5HO, made with a 10 inch wide housing, with the bulbs 7.5 inches apart. That light, sitting on top of the tank should give you about 60 micromols of PAR which would be medium to high light. When you get tired of battling algae you could raise it to 9 inches above the top of the tank and you should get about 40 micromols, which is a very good low medium level.
CO2 wont mess anything up unless you have high light and fluctuating CO2 levels. I think you will have about 30-35 micromols of PAR with no water in the tank or from about 35-40 micromols with water in the tank. (Water concentrates light and allows reflections from the glass to increase the PAR)
A couple weeks ago on my thread you posted a link to a chart showing the PAR's for CFL bulbs and noted that a PAR of 35 or below would keep me from worrying about CO2. At that time I was planning on using 14W bulbs but I ended up buying 19W bulbs. The bottoms of the round clamp light reflectors are about 17 inches from the substrate and the bulbs themselves are probably about 19. From the chart it appears this puts me at a PAR of about 35 but I thought I'd ask you to be certain. Also, I was thinking of adding a little DIY CO2 every now in then, will this mess anything up?
In case anyone reads the conversation I have with Hoppy below - these Coralife T5NO fixtures are growing plants real fast! It's not super bright and growth is a little leggy, but I have almost 0 algae (8 amano shrimp is the only kind of "algae crew" in there at this time and the only place algae exists is on the glass...plants wood are CLEAN) - I hung them 1" above tank.
Thanks Hoppy! Don't think I would enjoy trying to keep up with T5HO Growth at this time, maybe in the future, near or far, but this is great lighting for my first foray into planted tanks!
Hoppy. I hope you don't mind me sending this PM, but you seem very informed about lighting. I was wondering of you've heard of anyone with a 29 gallon tank, which is 30" in width, using a 24" light? It seems 30" T5ho are a little more rare. Thanks for any help! I appreciate it.
A good T5HO reflector used with T5NO bulbs, driven at T5NO power, should produce as much as double what a Coralife light produces. Great reflectors almost triple the light from a bulb. Coralife reflectors are poor.