Buying tankbusters and planning to rehome them when they get too large is NOT a good strategy. As you've found with the pet stores it can be quite difficult finding somebody who will take them, and a lot of the fish you have are quite sensitive and will not cope well with being shifted around once they are comfortable and established. You really need to start thinking about the welfare of your fish.
It seems from your sig that you have six mollies in a 30 litre (7 gallon) tank... this goes past insane, mollies need at least 15 gallons and this tank is as vastly overstocked as your main one. PLEASE move them, you WILL lose them. They could go in your other tank, once you remove all the fish from that tank that can't live in it:
The acaras will outgrow your tank, and they will certainly outgrow being in a group of 3 unless you've managed the considerable feat of luck of having them all of one sex. I strongly recommend you rehome them, as they will not get on with the krib, and they will eat everything in your tank if you want community fish in it. (If you keep them, there are not many other fish you will be able to have.)
The oscar, as everybody else has said, NEEDS TO GO. It is FAR too big for your tank, even as a juvenile you're having aggression issues with it and it's absolutely NOT suitable to keep with those fish.
The eels are predatory, they will outgrow your tank, and eat just about anything you try to keep them with, they've got to go.
The clown loach, plec and bala sharks are inoffensive temperament wise but they are far too large for your tank and will be miserable if you try to keep them in it long term.
The black ghost knife, in addition to being far too large for your tank, is an extremely sensitive fish as you've probably found out by losing two of them. Your tank is almost certainly not cycled because it will not be able to cope with this sort of fish load, and you need to find another home for the BGKF ASAP, or it will die as wel
The krib, corys and danios are ideal inhabitants for that tank. If you've only got one danio, you should get some more once you have rehomed all of the tankbusters above and cycled the tank. They like being kept in schools and are pretty and playful fish when there is a group of them. In addition to these fish, you could keep livebearers (platys, mollies or swordtails, but not guppies with a krib), some of the larger tetras (not small ones like neons with a krib) a bristlenose plec (other plecs get too large), harlequin rasboras and rainbowfish. If you rehomed the krib as well, you could keep just about any small freshwater fish.