Can't really answer that becos:
* As you can see, mine is a 4 footer & i have never try it on 3 feet tank.
* It also depend on ambient temp, heat load, etc..
* As for the noise, I think is acceptable.
16 months Resun Chiller for sale due to upgrading. Good for 3 feet & below. Selling at $250.00. Interested parties please pm me. thanks.
Model: CL 450
Capacity: 1/6 hp
Thermostat: Digital
The fastest & most cost effective way to raise mg (for me) is to use Epson Salt. It can be purchased from NTUC or Guardian. One box of epson salt cost about $3+ & it can increase mg level by about 100ppm for a 4*2*2! cannot remember exactly but you can refer to http://ozreef.org/diy/magnesium_additive.html. Hope this help.
I presume is ceramic ring. You should remove it slowly & at the same time, monitor your water parameters. The other thing to consider is whether your tank can handle the bioload w/o the cr & biohome that you are going to remove.