T5 for a 20gal

Alkalinity and Magnesium will also be used up by SPS.If you are lightly stocking you might be O.K. but every tank is different so answering your question is a guess at best. Please don't hijack the O.P.'S thread if you have any more questions please start your own. Thanks and good luck!!

 

Seeing as you're new, I would suggest not worrying about SPS corals right now. they need near perfect water parameters, and can be a pain if you're just starting out. As far as lighting, if it's a 20H, and you plan on keeping softies and some low/medium light LPS, I would go with a good 24" dual bulb setup. Don't have to get crazy fancy and spend 300 bucks on one. Just something decent. This is more or less so you get a feel for sw tanks.

Now, I'm not saying go buy the cheapest fixture you can find, but don't go spending crazy money either.

If it's a 20 long, then a 30" 2 bulb would be more than enough to get you started with.