Moving fishes to another community

I have my main freshwater tank (250 gl) with 2 rays, 1 clown knife, 1
reelfish, 2 bala shark, 2 otocinclus and 8 gouramis.

It's kept at 27ºC, and filtration and water quality is ok.

Also, I have a 20 gallon with a koi and a goldfish (which are overgrown for that tank) allong with two middle sized angles, a platy and an albino corydia (¿?) catfish. I feel this is overstocked, and I want to move some to the bigger tank.

My first idea was taking the koi and the goldfish since they are the bigger ones, but the temp may be too high for them. Am I right?

Plase, need some suggestions here.
Below this is a link to some pic of the big tank. May help. Thanks in advance.

The small tank is unheated since it's in my bedroom and temp is always the same. Right now, the water temp is 22 ºC.

What I see is the the GF is too active. He goes like crazy from one side to the other, bumping into the other fishes.

Maybe taking the others to the other tank will help. My feeling now tell me to leave only the gf and koi in the tank.

Thanks for advice. The link in an free server witl limited disk space and bandwith so (I think) they sometimes disconnect it to encourage you to pay.

Try again. It's working for me.

Stingrays are moderate-difficult to keep. They are somewhat shy until very well aclimated. They are venoumous fishes and you must be careful when putting your hand in the water cause you can be stung. Their poison is not entirely known, and since there are a lot of species with LOTS of variant it's unsure if an specific individual can be fatal or just exrtremely painful. So, not a good fish when there are children messing up.

What I have are Potamotrygon Reticulata or Reticulata Freshwater Stingray, which is hardier and less shy than other similar species.

The main difficulty in keeping stingrays is the size of the tank, which has to be at least a tempered 90 gallons for a couple of 4" baby rays, to provide enough swimming space and water volume to compensate for the LOT of waste these carnivourous fishes will leave behind. Also think about over filtration and more frequent gravel cleaning.

Then, to keep them healthy you have to give them plenty of meaty food, like tubifex worms, earthworms and some small feeder fish like gouppies. (A LFS owner stopped selling me gouppies when she found out I was using them to feed a ray. I believe she is a good person and kept the value of the fish life over the money. I still buy from her.)

I'd recommend to read a little about these wonders. You can even buy some $10 books from amazon and learn a lot.