DIY metal halide light fixture.

No, you need a ballast for both type.

Check out craigslist for local business selling their shop lights. Most of them are 400w metal halides and all you have to do is change the bulbs to what you want. Thats what I did on my setup. I bought mine for $25 a piece and just bought the reflectors and was done

if you have a 400w ballast dont put in a 250w lamp you have to match lamp to ballast

$70 for a ballast, lamp, and reflector is a bit cheap for brand new... I'd be weary of it.
 

you'll most likely have a capicator also, many ballasts are multi watt, meaning there are like 4 wires to power it, if you hook 1 wire it is 250 watt, 2 wires is 400 watt and so on

they are multi voltage not wattage they can be 250w,but 120v,220v 277v

I did the same thing - I bought a couple of MH lights on craigs, made the reflector out of stainless and changed the bulb, voila! 400 Watts of metal halide goodness X 2. All for less than $100. There are two types of ballasts as well. There's an electronic ballast and a magnetic ballast. the electronic ballast looks much like a flourescent light ballast. Long and skinny usually. They don't require the starting capacitor. The magnetic ballast looks more like a transformer and needs a capacitor. Most of the lights you will find on craigs will have magnetic ballast. There's nothing wrong with them. they just "hum" a bit. Electronics are more expensive. They will both get quite warm - this is normal. the bulbs will get downright HOT - be VERY careful you don't splash water on them or they WILL shatter and you will spend hours picking the glass out of the aquarium.

 

as stated above, don't mix bulbs and ballasts. If the ballast is for a 400w bulb, don't put ANYTHING else in the socket. most of the ballasts you will find on craigs are, as mentioned above, multi-VOLTAGE, not multi-AMPERAGE. make sure to use the right leads for your output - which would be 110 I bet. using the other leads doesn't mean you can drop the wattage of the bulb. bad idea.

 

Good luck!

What are you planning on keeping in your 125? Honestly PC(power compacts) would be a waste of money spent...bulbs aren't cheap, and what you think your saving your really not. If you want T5's a way better choice any way you look at it.

I see the watts per gallon rule being thrown around quite a bit.  But watts are not what are important when it comes to reef tanks.  Lumens are more what you're looking for.  I can put the same, if not more light into a tank with 288watts of the proper sized LED's than I could with 500watts of Metal Halide.  Power Compacts don't put out near as much light as their T5 cousins, nore do they penetrate to the same depths inside the tank as far as coral growth is concerned.

 

Like, Acrylic51 mentioned or is inquiring about...alot of what your lighting requirments will have to be shall be determined by what you plan on keeping in your tank.  If you're planning on doing fish only then Power Compacts are fine.  If you want to do mixed reef then look into a good T5 fixture or a T5+Metal Halide combo.  LED's are becoming very popular but they are still very expensive for the type of LED's that you need for a reef...but if you can build your own rig then the cost is more comparable to a good T5 or T5/MH combo.  Or if you're one of those people who are supper rich and don't mind shelling out multipule thousands of dollars for lighting then I hear some headway is being made in the Plasma arena.

Thanks Corey!!!!! Scary when someone actually knew what I was referring too!!!!!!!!
 

 

You're right.... I had it backwards, thats why I had help with the wiring
 

The bad thing about lumens is a tester is so expensive thats why people want to use watts per gallon

 

its important though to know you cant compare MH watts and PC watts