Lighting a 20 long

[Aqualady40]

Hi. I have a 20 long that is about 12 3/4 inches high. My substrate is 2 inches thick. So, if I subtract 2 inches from 12 3/4, that would leave 10 3/4 inches to light. I have 2 CFL 13 watt 6500k in metal shop clip-on lamps. My question is, "How close, in inches, should the lamps be to the water to get good/strong medium lighting?

 

[Old Scales]

You should be in solid medium light with that height. IMO.

 

[Aqualady40]

I never said where the lamps are. I was giving the height of the tank, the depth of the substrate, and the distance from the top of substrate to top of tank...My question was how close to place the lamps to get strong medium light? For example, 2,3,4, etc inches away from top of water.

 

[Old Scales]

OK. Sorry about that.

 

[Aqualady40]

OK. Sorry about that.

oh its okay, do you have a suggestion how close to place them?

 

[Old Scales]

MY reply dropped off, lol I'll try again. If the CFL cones are the real shiny type inside and not the frosted finish type, you should have medium light out to 14" from the substrate. Brian_Nano12g is the light Sen-Se in here. I haven't seen him in here much since his apt. fire. Hopefully someone else will chime in soon. OS.

 

[Fresh2o]

One thing to consider is the size of the cone and light spread relative the surface of the tank. If you use the smaller size cone (5.5") and if it is close to the surface, it may result in darkened areas of the tank. Of course, elevating the cone will resolve this issue (but decrease PAR). Or you could go with larger cones (8.8" or 10") and probably move the them closer to the tank.

I know this does not answer your question regarding distance. I just wanted to add cone size and light spread as factors in making your decision.