MH over a 20 gallon...

[X-Treme]

I'm gonna set up a 20 gallon tank and would like to keep anything I might like including small clams. Is a 150MH anough or should I be looking into a 250?

[Chowder]

Î would go with the 250w. It will give you more options on what you can keep. Clams tenitively do better ( keep there colour) under higher intensity of lighting.

[andsoitgoes]

I've got a 18" deep setup (44g cube) and I know a clam would do fine, but I've also accepted that the thing needs to be real darn close to the top.

Most 20g tanks are only about 15 or so " deep - but having a smaller tank you'd probably want the light higher up, so going 250 would give you more options.

Is a small clam the only "high light" animal you're wanting to keep? Are you planning on doing softies, SPS? LPS?

[X-Treme]

I have a few LPS and SPS undr 96W PC lighting in a 10 gallon right now all doing quite well.

[Fugu]

Maby 175,250 seems like a little mutch.I am puting 14k 250watt MH on my 30tall and it seems like plenty.

[midgetwaiter]

I think you need to take this a bit further and think about what kind of bulb you want to use. A 10000k 150 watt HQI would work just fine for most things provided you are either happy with the colour of the bulb by itself or you had a way to add actinics.

As soon as you think to yourself, "I'd like to try a 14k bulb in there" you're screwed as far as crocea clams or demanding SPS goes. You will see a drop in the amount of light in the correct wavelengths for photosynthesis (measured as PAR) the higher up you go in colour temperature. The drop in PAR between a 10000k bulb and a 14000k bulb can be nearly 50%. If you want to use a bluer bulb you will need the 250w.

[X-Treme]

I think I might actually get a custom tank made to better suit the light because the light is 15" wide. I am thinking a 24"L x 15"W x 18ish" deep (need a DSB for my yellowhead jawfish). And BTW the lighting is 10000k and it comes with two colors of actinics. 2 24 Watt t5's of each color(420nm and 460nm)

[midgetwaiter]

That simplifies things then. Somebody with more SPS experience may correct me on this but I think you could go with either unit and be happy.

The 250 would give you the option to put your high demand critters almost anywhere where with the 150 would still require a bit more planning and be less flexible. Really fussy stuff would still want to be high and centered. On the downside with the 250 you'd have to be careful with acclimating new additions and some things like zoas and mushrooms would be difficult to place.

[imisky]

what size is "small" in your opinion, because clams that are 1-2" does not depend on light as much as they depend on live food as there mantles are too small

[canuckzilla]

I've got a twenty and have eventually settled on a coralife aqualight pro which has made my tank very happy. It's provided me great versatility in how I can stock the tank and in turn the reef has been thriving...not just surviving.

Built into the light:
One 150 watt 10,000K double-ended HQI metal halide lamp
Two 65 watt True Actinic 03 Blue square-pin compact fluorescent lamps
Two 1 watt Lunar Blue-Moon-Glow 470nm LED lamps


Product Link
http://www.esuweb.com/cardfile.asp?ItemNumber=53502&IDProductRelationship=313

No doubt, it was pricey but for me it was worth saving up for it given what I wanted for both looks and effectiveness.

[OCDP]

I use a 250w HQI Giesmann Nova II over my standard 20g tank. Things get a bit tricky when using this much light over such a small tank. I have used everything from 2x65w PC's to 150w HQI to the Aqualight Pro, and settled on 250w HQI. Why? Because this way when I upgrade I will have the proper light I need/want. Secondly, I just like to have lots of light... your corals will thank you, the growth is awesome and I just like the look of a bright lit up tank.

Obviously with this intensity you face other problems ... evap, temp swings, burning corals, etc.. but it's not so bad. Summer time is my biggest problem... it's really hard to keep temps under control, so I usually add a fan to the mix, then face evaporation issues. In the end.. I'm happy with 250w HQI and so are my inverts (clams, anemones) and corals (I keep LPS, softies and SPS) . I'd say go with whatever you can afford.. if you can afford 250w ,go for it. You can always adjust the height of your light ,etc... then, if you do upgrade in the future.. you may already have the proper light for the system.

[canuckzilla]

So here's the next question for those having MH on a 20g tank. How high do you keep your lights from the top of your tank?

I have a 10k 150w and keep the lights 10-12 inches from the top. At 8 inches or lower, my coral was getting burnt near the top of the tank.