ideal hight of MH

Hi. For me, there are two main considerations - heat and splash.

The intense heat from MH - especially for a smaller tank like yours means you will have a heat problem if the fitting is closer than about 30 cm as the beam will gradually heat the water. Not a big deal if the room is cooler than the tank, but in Summer when you are at work and the house is locked up might result in very high water temperature in the tank. I might even go a bit higher as the depth of the tank is not so great and the light wont be attenuated much by the air above the tank anyways. Do you have a glass cover on top ?? If so, then if you keep it very clean, the above advice still applies .

I assume you have a light cover to protect the MH bulb from splash. Unlikely to be an issue at 30 cm height (though still recommended) , but if you want to be closer to the water surface, then it is mandatory.

Cheers

That's a good response. There is no specific answer, it depends on what you want. You made no mention of plant types, density, desired results, etc. These may affect the proper distance.
I'd start with 10"-12" and vary from there depending on what you see in your plants and tank temp.

cheers,
joel

Thanx guys for the reply's

I am planning to keep discus in a heavilly planted tank, so the temperature is not a very big issue(for the discus).

There is an thoughned glass cover on the fixture so i am not worried aboud splas water also.

What i am scared of is "burning" some waterplants. I used to run an saltwater tank, that meant that my corals tendet to burn (bleached) closer to the surface.
Do waterplants suffer from the light intesity or do they just love it? (depends a bit on plant specimen i quess?)

thanx,

wouter