Lighting for New Tank

[Clare]

Hope that someone can help me with the following questions.

I recently set up a 115G freshwater - 24" deep x 60" length x 18" wide. Doing lots of research on the web gives me tons of info, most of which is more technical that I can relate to.

I already had a 48" T5 HO Coralife fixture with two 6700K bulbs so that is current what it on it. I also recently ordered a new 48" 4 bulb T5 HO Coralife fixture and plan to put in all 6700K bulbs (it comes with 10K and actinic and two blue LEDs).

Will this be sufficient lighting for most low to moderate plants? I am not planning to put in a CO2 unit. If I figured it correctly I should wind up with 2.8W per gallon, though I see from my reading that the watts per gallon rule is generally not a totally sufficient guideline - is this true?

Finding reasonably priced 60" lighting was nearly impossible and I am not the DIY type for the most part I figure I would just plant my higher light plants in the middle and leave the ends for the the plants that require less light - or I could just stagger the fixtures....btw, the pic I uploaded shows additional Coralife fixtures that I recently sold.

Thoughts, please?

Thanks tons,
Clare

 

[jetajockey]

I've got a 48" light over mine and it works out fine, it does get a little less coverage on the 6" of each side but it's not too bad. If you plan on running all four bulbs you may have issues if you don't add co2 along with it, but I'd just play it by ear and adjust accordingly.

 

[Clare]

Thanks for the reply - it's good to know I didn't make a bad choice on the lights after all

As a newbie, can you elaborate on why the CO2 would help if I run all four bulbs? Am I going to get too much algae build up? I have four SAEs int he tank now and they are doing a back up job on some of that stuff LOL

Thanks again!

 

[jetajockey]

Welcome. With 4 bulbs the light intensity is going to be really high, so Co2 supplementation is probably going to be necessary. This depends on a lot of different factors, so not every tank is the same, but here's a general guideline to give you an idea of what kind of lighting you'll be dealing with.

Light fixture brands vary in quality and some are better than others but as to an exact measure of how much better/worse, its mostly speculation. This chart assumes that the fixture has nice reflectors on it, so for a low-end commercial product that doesn't have individual reflectors for example, the output would likely be a bit lower than what it says on here.

PAR vs Distance, T5, T12, PC - Updated Charts

This is the gist of planted tanks, there are 3 things that your plants need, light, co2, and ferts. There is an ambient level of atmospheric co2 (a very small amount) and also some that is generated in the tank itself, but its all relatively small. Also, tap water has a lot of micronutrients and even some macronutrients in it, so it helps cover some of the fertilizer aspect.

It's a big balancing act, a low intensity light setup will grow the plants slowly, but in turn, demand far less of co2 and ferts as well. The higher intensity your light setup is, the more demand for co2 and ferts, so at that point you have to start adding co2 and fertilizers to keep up with the demand put forth by the lighting.

If you don't, then you start running into plant growth issues and algae issues since algae is less demanding than plants are when it comes to needs.

SAE's are great algae eaters but they will never be able to keep up with the algae production of a unbalanced planted tank, unfortunately.
Hope this helps.

 

[Clare]

Thanks again for all help - looks like I have some reading to do ... I will probably wind up adding CO2 so that my poor little SAEs don't have to work so hard

Cheers,
Clare