Aggressive Female Dalmatian Molly

[alylah]

Hi there,

Last week we bought a 29 gal tank. After setting it up and letting it filter for that week, we got our fish last night. We have a pearlscale goldfish, two lionhead goldfish, a red-eyed tetra, a colored tetra, an angelfish, a dalmatian molly and another small little molly, but I'm not sure what type.
We did everything as the petstore said, letting the bags containing each fish sit in the tank for 15 minutes, then mixing the water for ten, then letting each fish out.
All the fish seemed great, active and exploring the tank. After a few minutes though, I noticed my molly was chasing the 3 goldfish, bumping into them nibbling at them. I didn't really think anything of it at first, but she kept chasing them and getting increasingly more aggressive. She seemed to leave the other fish alone, maybe a couple pecks but not as aggressive as with the goldfish. After about half an hour I removed her from the tank and put her in a smaller fishtank, I'm guessing it's around 2.5 gal.
I called the manager of the petstore this morning. He told me to re-introduce her to the big tank later this evening and see if there's a difference. I did internet research as well, and the most commonly suggested actions to take are changing the tank around, putting the molly back in after a day or two, and taking the fish back to the petstore. Unfortunately, the petstore won't take animals back.. So I'm left to try and fix the problem myself.
I was hoping I could get some help from this site as to what I should do.
Thank you in advance to anybody who can help me!

 

[BlaseMrNiceguy]

This may be stress but, I hope you don't take this the wrong way, you need to be filled in on some things. Your goldfish will need a bigger tank as well as the angel fish. Also you need to learn about cycling, more specifically the nitrogen cycle. You will be doing what's called a fish in cycle. The mollies and other fish should be ok in that tank. Mollies generally need at least 3-4 to be happy generally 1 male to 3 females. It sounds like you may have a male Molly but I can't be certain without a pic. Also look up drip acclimation it's really the best way to get your fish ready for your display tank. Goldfish, if that's what you have, need to be fed a lot more often than regular fish as they have virtually no stomach. But you may have oscars, either way they have a huge bioload and will require multiple water changes a week.