suggest lighting for a 15 inch cube

I just posted a nice reply and lost it (!@#!$$#!$)!

Okay second try but less verbiose lol

Do not go over 15-20 watts TOTAL for this tank.

Try and mount the fixture so it can be adjustable.

Any decent compact flourescent (CF) bulb between 6500 and 10,000 kelvin based on your choice should be fine. How it looks to you, as the plants do not care.

I don't think you will need a T5, but small tanks are not my area of expertise.

Remember that any reflector will really enhance any light. This is not a large tank, so it is easy to overwhelm it with light.

It is easy to have issues related to too much light. Higher light drive higher rates of growth and more need for all nutrients, esp c02.

Hope this helps.

 

Two of these: Compact Fluorescent Aquarium Lighting: Mini-Freshwater & Mini-Aqualights is what I would be looking at if I had that tank. You need more watts per gallon for tanks that small than you would expect. If you have good DIY skills you could use the guts of these fixtures fitted into a DIY hood, possibly with a better reflector, and suspended over the tank so you could raise it a bit if it is too much light.

 

A lot of people use the midday light surge as you are planning, but my preference is to use the same light all day. If you are suspending that light above the tank you don't have to raise it very far, just a few inches, to reduce the intensity a great deal. Oregon Aqua Design | Come in we are OPEN!!!! is one option for suspending the fixture.