Light Height

[waterdrop]

Why are the lights on so many planted tanks sitting way up on stilts?

 

[garuf]

Because they're designed to be around 10cm away from the water surface to ensure that the allow maximum light distribution through the water column.
Oh that and they look nicer than having them sitting on the tank rim where you run the risk of cracking the glass.

 

[waterdrop]

Thank you garuf.

So many planted tanks I see have completely open tops. Is there one of those hard to get around problems between completely open being good for plants but allowing fish to jump out?

 

[Revision17]

I've only had a fish jump out of the tank once. That was a burmese boarder loach, after I did a 3 day greenwater blackout. I turned on the lights, saw the water was still green, turned the lights off, threw the towel over it again, and the loach jumped.

The only reasons for open tops that I can think of for open tops is because it looks pretty (yes.. it's subjective.. I like the look) and you can aquascape the tank with the lights on (which makes it so much easier).

 

[Colin_T]

Lights are sometimes mounted higher than the tank so plants can grow out of the water and still get some light. If the lights are resting on top of the tank then any plant that makes it out of the water will no longer get any light.
Open top tanks allow mor light into the tank. Coverglass can reduce the light levels in the tank, especially if they aren't spotlessly clean.
The other reason lights are mounted above the tank is to allow better air flow around the light unit. The cooler the globes the longer they last. It also helps reduce the tank's temp from rising due to the heat from the light unit.