I have a 24 gal tank with a 150w MH and I have no temp problems. If anything, it gets too cold! I just keep my ac unit at 74 during the day when the MH is on and point the vents straight at the tank. It doesnt get above 80. At night, I put it to 76 and move the vents away from the tank, and it doesnt go below 77-78 (sometimes not even that cold.) If you dont have a good AC vent near the tank, you may need a chiller. But before you do that, see what the temps will be like. Dont get any fish/corals anything yet, and test it for a little while (unless you already have some.) Do it a day or two straight when you can be home all day to watch the temp. If it gets too warm, put a fan on the tank (straight on the water.) This may help keep it cool. I had really bad temp problems when I had the stock hood on my AquaPod. It was near 87-88 degrees!! I then bought a new window unit AC ($250) and went topless with the MH and now its perfect. I also have a 20g long with 130w PC lights and hood (open back) and that gets much warmer than my tank and the MH. You can keep just about anything I believe. I have SPS frags, a clam, softies, a brain and all are doing great, but water quality has a lot to do with that also. About the filter, I dont know about that. I am currently making the rear of my tank a mini-fuge with live rock rubble and chaeto. And I replaced the powerhead on mine with a MJ. Its great. I dont trust anything stock now, everything on my tank has been gutted and replaced except the glass and plastic
You just need hose clamps and some vinyl tubing to connect the powerhead. Depending on how much movement you want, I'd go with a MJ 900 or 1200 if you want to use only one, or maybe a pair of MJ 600, or a combo of any size, its personal preference. I cant tell you about the filter, I have the mini-fuge and also an AquaC Remora (which I HIGHLY recommend!!) I just got one off the big auction site for $106 brand new (it had a scratch, big deal!) I'm keeping this one for a future tank, I just couldnt pass up that deal. Anyway, good luck!!
-Melody
My tank: