Hi ohioballer,
Welcome to the board!
First things first.....if you don't have your tank set-up already, I'd suggest not using the undergravel filter. Although they are very useful in fresh water tanks, they're liable to cause you problems....down the raod in a sw tank.
There are a number of filtration options available to you: canister, wet/dry, refugium, etc. you may want to do a search on this site to get some more information on all of them before you proceed to purchase one.
Have you decided what you...ultimately...want to keep in your tank? If not, give that some thought. Will you have fish only; some coral; coral only; coral with clams? These choices will influence other choices you have to make, particularly what kind of lighting you need. Again,a search on "lighting" ( NO, VHO, PC, and MH) will provide you iformation about each.
You will be better off, regardless of your ultimate choice of livestock, if you include live rock in your tank. Most sw creatures need places to hide and live rock provides that and assists in your biological filteration. You'd also do well to consider live sand as the substrate. It, too, will assist in filtration.
Once you've made all these choices and set your tank up and added the sw , from de-inonized or reverse-osmosis water....then you need to add a cocktail shrimp to help your tank begin its cycle . The decaying shrimp puts ammonia into your tank which will initiate the cycle which your filtration system (filter, lr, ls)will
over a period of weeks, breakdown.
You'll need some test kits for ammonia, ph, alk. A good skimmer is necessary but only after your tank is established and you have some fish in it.
Wow! Sorry to be so long-winded. There's alot to learn. Don't hesitate to ask questions and keep posting!!
good luck
Jim
