Lighting advice

[Delphinus]

Planted tank is a 30g. Currently lit by 4x20W daylights. There is something wrong with the ballasts though because lights don't seem to last longer than 6-8 weeks (then only light up at half intensity, or worse, they don't light up at all).

Been thinking about what to do about it. Could replace the ballasts, or, I could use the oportunity to upgrade to something else.

Wouldn't mind one of those aquaspacelights. Only issue is they're about $200 for the 30" version. That would be 110W, a 30W increase from the current 80W (and I expect a significant improvement in lumens too going from NO to PC).

Another option is that I have a spare 150W HQI ballast and fixture, and spare 6500K bulb. I could shoehorn this in the hood. An attractive option because it's free since I have all the equipment already; only downside is that it's a HUGE increase in lumens going from 80W NO to 150W MH; and I would expect there to be a heat issue as well (I expect I may need to vent the hood, but that's not a big deal).

Is there any reason to NOT go to the metal halide?

I do want to get more plant growth on this tank, maybe get into some of the red leaved plants, and just generally increase the diversity of plant life. I've heard that more light in a planted tank is mostly lost benefit if you don't have CO2 but I am planning to go CO2 from now on. (I haven't a clue what I doing yet, but that's a different issue. )

[trilinearmipmap]

First of all I suggest don't go metal halide it is overkill for this size of tank, you will run into algae and nutrient balance problems. IMHO metal halide for this size off tank would only be appropriate for very high light demanding plants and I wouldn't do it even then.

I would suggest a single 55 watt AH supply pc and DIY CO2. Although nominally less than 2 watts per gallon, with the AH supply reflector this should be more than enough.

Examples of lighting I have over plant tanks that work well:

Triple tube NO 3 x 30 watt bulbs over 33g (36") tank, no CO2
2 x 55 Watts pc plus one x 30 watt NO over 58g (36") tank, no CO2
4 x 55 Watts pc over 75g (48") tank, CO2 injection

As a rough idea, 3 normal output bulbs or one pc bulb over the length of your tank, without CO2, should be good.

After some experience with high-light CO2 injected tanks and low-light no CO2 tanks, I enjoy the lower-light approach more. The low-light tanks are more beautiful, less maintainence, and less stress.