Is it true that Rosie Reds & Comets cannot be kept in the same tank together? Recently I bought one 1 1/2 inch rosie red and one 1 1/2 inch comet. I have quarentined them both for 2 weeks. I would like to put them together in one temperary 5 gallon, and soon into a ten, but the employees at the pet store say I can't, but they didnt explain why. In the spring I will put them both in my 200 gallon pond.

If they are both healthy and of similar size, they will be fine together. Rosy reds that are sold as "feeder fish" are often diseased so one risk is them giving something to the goldfish. If you've already quarantined, and they seem fine, that's less of a worry. Larger goldfish can eat smaller rosy red minnows. That's not a worry if they're the same size, at least for now. In a larger pond, it's easier for smaller fish to escape larger fish.

I think they should be find together for now. As with any fish mix (even among the same species), keep an eye out for either fish harassing or picking on the other. A solitary rosy red should be pretty docile, especially if female. Goldfish can pick on other fish sometimes and are always curious.

Thanks for the advice, right now they're swimming happily together. I have another quesion for you: I recently got a 10 gallon fish tank at a garage sale. I wasnt sure if I should use it just incase there might be a bacteria, soap, or some other harmful residue in it. Is there anything I could do to make sure there isn't?

You can soak the tank in dilute bleach to kill anything living including bacteria. That won't necessarily remove any inorganic toxins that may be in there such as leftover salt, soap, etc. After soaking the tank for a day in about a cup of bleach and the rest water, drain it, rinse well, and refill with fresh water. Add a double dose of dechlorinator to that and let it soak another day. If there appears to be hardwater or salt deposits, you can try to scrub them off with some acid such as vinegar (acetic acid). Be sure to rinse well. Dump out the dechlorinated water and then start fresh.

I would really like to get a 3" goldfish (comet I believe) for the 10 gallon fish tank with the rosie red and comet (both around the same size). If I did get another goldfish would it eat the rosy red? Would it be better to put the rosy red in a 2.5 gallon fish tank, get him another rosy red, or keep him in the 10 gallon with the 2 comets (with a couple rosy reds if the aquarium store is still selling them) like I said earlier in the spring they would all go into my pond.

Ideally, you would have at least 10 gallons for each goldfish, more when they get huge. While small, you can certainly keep more as long as you have plans for a larger tank or pond one day as you do.

If you really want another goldfish in your 10 gallon, I do suggest moving the rosy red to its own tank, although 2.5 gallons is pretty small. A goldfish is probably going to be over 4" before being able to eat a one inch fish. Goldfish sometimes deliberately eat smaller fish but sometimes, it's by accident.