Some answers:
Sponge filter:
no particluar model or brand. It is one of the cheapest filters you can buy. If you go to any
LFS and just ask for a sponge filter, they should have it. Costs typically around US$10.
PVC Pipe:
Ideal because it is chemically inert. Use a section of 2" Schedule 40
PVC pipe available from any hardware or home improvement store. Cut a couple of 6" sections with a hacksaw or any fine tooth saw. Clean well and you are ready to go.
Fresh vs. tank water:
IMHO, I would use fresh saltwater versus from your tank. I tried that route but ended up adding water that was too nutrient rich to my
QT. Remember in the
QT you do not have the bio-filtering capability of your main tank. Opinions on this will vary.
Seeding your filter:
You can just place a spare sponge filter (tie it to a piece of rock or something to keep it from floating away) in your main tank. As long as it is exposed to your main tank water, it will culture the bacteia.
HTH. Good luck. 8)