150gal tank

[paulhrone]

hi there ive just set up my 150 gal tank and im running 3,08 w/gal will this be enough ive run a smaller tank with about 3 and thats been fine how ever ive read some where that bigger tanks dont need as much light is this true
cheers pau

[spypet]

Originally Posted by paulhrone

how ever ive read some where that bigger tanks dont need as much light is this true, cheers pau

the current consensus is that is true, however don't worry that 3wpg is too much light over your 150g as bulb light output degrades pretty quickly, so the average light you'll get over the life of those bulbs will be considerably less than 3wpg. also keep in mind that a 3wpg 150g tank may also require compressed Co2 so your more aggressive plant growth can help keep algae at bay. if you do not have Co2 planned, you may want to consider reducing the number of hours during the day your light is on and/or being much more careful regarding your tank chemistry in order to keep algae away.

[paulhrone]

i have thought about co2 and have tried it in my other tank how ever i might try it also on my first tank one of the student at my local uni made me a light prison which has been great so he,s designing me a much bigger one for this tank
i still dont understand why bigger tank dont need a much wpg though

[GDominy]

I ran about 3.4 watts/gallon over my 135 gallon tank, and I was able to grow most plants fairly easily WITH compressed CO2. However, I did find that plants at the substrate struggled considerably more then the plants in the mid level to upper level of the tank.

I'm not sure why, to this day if it was a light intesity problem, or what... For all I know the faster growing plants were choking them out. I will say this though, Java moss grew very very well when it was located about 12" from the light bulbs.

[ringram]

It has to do with light intensity. 3.4wpg of T-12's isn't as intense as 3.4wpg of T-5's or MH's. PC's are probably somewhere in between. If plants at the substrate were struggling, the light level and/or intensity was simply too low.
I also hear some people throwing around the notion that larger tanks don't need much wpg. Be careful how you word that. It depends on many things, like light intensity, plant type, available nutrients, Co2 level, depth of tank AND the actual wattage of light being used.
A small tank of, say, 20g may require 3.5wpg to grow a certain plant well (everything else being equal), whereas a tank of 125g may only require 2.5wpg to get the same results.
I also remember hearing that deep tanks (>24") may require more intense lighting to have much success at all. That is why it was explained to me that you pretty much need to have T-5's or MH's with deep tanks, simply because the other lighting types aren't intense enough to penetrate to that depth. Exactly the same reason that many serious reefers go with very intense lighting, like MH's and T-5 HO. Us planted tank folks are in a similar situation. Just my $0.02.