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ideal hight of MH

1303 Views 3 Replies 3 Participants Last post by  wfvanwielink
hello guys,

here a question from Holland:

what is your opinion on the ideal hight of the fixture above waterlevel?

I run an 150watt aquamedic MH fixture above an 100x60x60(cm) tank

I am currently waiting for my Dennerle HQI bulb from my LFS.

greets and thanx,

Wouter van Wielink

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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.

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.

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?)


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