Metal Halide for 90cm (36") deep tank

[f1ea]

Hi guys, i need your help/guidance here.

I am planning a custom built 90cm H (48"L x 24"D x 36"H) tank with low light plants and no carpets ie = Low maintenance, No CO2 inyection.

The hope is to use Metal Halide lamps, I am thinking 2x 175W metal halides.

Plants will be Java fern, Anubias, Crypts, Moss etc near the bottom with maybe some more light demanding plants near the top...

Does anybody have an idea, how high above the water surface should i hang the lights to achive the above w/o inyecting CO2 (doesnt have to be a precise number, more or less a range would be nice so that i can plan on the lamp fixture)?? any other suggestions?

Thanks very much in advance!

[xmas_one]

You might consider using co2, or using different lights. In my experience, MH + lack of co2 = tons of algae. If you're dead set on no co2 and MH lighting, I'd say hang them high ~18" and then slowly lower if you're able to keep the algae at bay. Good luck, that tank will look awesome with the light shimmering down through it.

[f1ea]

Thanks!
Hmmm I wouldnt mind having them at 18". That's a number I wanted to have some guide about for clearance, lenght of tubes and so on with the fixture... let's say between 16"-20".

But I would want to have no CO2. If i were to get interested in carpets (maybe Marsilea), then I could go with CO2. I'll think about it though... it all depends on the scape/inspiration........ but I really want low maintenance, little trimming, etc

[MarkMc]

I know this is not the answer you are looking for. I had 2 MH 175 watt fixtures over my 55 gallon for a long time and let me tell you there is nothing like it. It is beautiful but... you are not going to be able hang them high enough. I had mine hanging around 18" above the tank. 20 lb tank of CO2-2 1/2 foot by 6" high tech homemade CO2 reactor and a bubble rate too fast to count. I now have 108 watts of T-5HO hanging 18" above the tank-now I can manage my tank. I still run CO2 at a high rate too. You aren't going to get a horse to change colors...2 175 watt MH pendants is going to be high light unless you are planning to cut holes in the ceiling to recess them (just joking-don't put MH fixtures in your ceiling).

[Hoppy]

A 36 inch high tank can be adequately lit with T5HO lights. The 24 inch front to back depth makes it necessary to use at least two two bulb fixtures, preferably 3 or 4 bulb fixtures, separated by about a foot. I'm not recommending that, just offering the information.

[f1ea]

Originally Posted by MarkMc

I know this is not the answer you are looking for. I had 2 MH 175 watt fixtures over my 55 gallon for a long time and let me tell you there is nothing like it. It is beautiful but... you are not going to be able hang them high enough. I had mine hanging around 18" above the tank. 20 lb tank of CO2-2 1/2 foot by 6" high tech homemade CO2 reactor and a bubble rate too fast to count. I now have 108 watts of T-5HO hanging 18" above the tank-now I can manage my tank. I still run CO2 at a high rate too. You aren't going to get a horse to change colors...2 175 watt MH pendants is going to be high light unless you are planning to cut holes in the ceiling to recess them (just joking-don't put MH fixtures in your ceiling).

Dont worry. All opinions are welcome! yours is very interesting actually.
I do have LOTS of clearance to raise the lights as much as I want (the house has high ceilings); I could also make the tank a little bit deeper (front to back). The idea behind having a good estimate to know how high the lights need to be is more or less to be able to design the mounts and/or hangers...

A 36 inch high tank can be adequately lit with T5HO lights. The 24 inch front to back depth makes it necessary to use at least two two bulb fixtures, preferably 3 or 4 bulb fixtures, separated by about a foot. I'm not recommending that, just offering the information.

Yes, T5 is the other option.
In my case, I want to avoid T5 because the boxier fixture creates more heat and a couple MH lamps would have a simpler and sleeker look. Maybe a good T5HO alternative would be 4x 54W. This is about 1WPG of T5, which is not bad for low light. Could be raised as well...

Thanks both!

[MarkMc]

The only issue you might have hanging the lights really high is the annoyance factor of very bright lights in your eyes. MH and T-5 HO lights are really bright-not the type of easy on-the-eyes lighting that we typically light our rooms with. But sometimes we must suffer for our hobby lol.

[Dr. Acula]

Originally Posted by f1ea

In my case, I want to avoid T5 because the boxier fixture creates more heat and a couple MH lamps would have a simpler and sleeker look. Maybe a good T5HO alternative would be 4x 54W. This is about 1WPG of T5, which is not bad for low light. Could be raised as well...

A MH lamp is definitely going to get hotter than T5 HO, but I do agree about the sleeker look. And, in general, the WPG rule is garbage. It just doesn't really apply to T5 or T5 HO fixtures.

But anyway, if you're set on the metal halides, you can purchase light filters and position them under the lights. They come in a few varieties to block a certain percent of light. You wouldn't be able to position them directly under the MH fixture, because of the heat, but I'm sure it could be worked out. I think I remember someone on here saying that that's what they did at some point.

[f1ea]

Originally Posted by MarkMc

The only issue you might have hanging the lights really high is the annoyance factor of very bright lights in your eyes. MH and T-5 HO lights are really bright-not the type of easy on-the-eyes lighting that we typically light our rooms with. But sometimes we must suffer for our hobby lol.

Yes, that's what i think. Its really annoying to get the glare when in front of the tank. Maybe it could be improved by tilting the light a little bit. I can make a test before fixing the lights to see how much of a glare there'll be.

A MH lamp is definitely going to get hotter than T5 HO, but I do agree about the sleeker look. And, in general, the WPG rule is garbage. It just doesn't really apply to T5 or T5 HO fixtures.

But anyway, if you're set on the metal halides, you can purchase light filters and position them under the lights. They come in a few varieties to block a certain percent of light. You wouldn't be able to position them directly under the MH fixture, because of the heat, but I'm sure it could be worked out. I think I remember someone on here saying that that's what they did at some point.

Yeah the WPG is garbage. Specially with MH/T5HO, and tall tanks... the filter may not be a bad idea either. Or instead of 175W i could get the 150W lamps...

Wow, I didnt know MH was THAT powerful.......