hi mate , unfortunatly bleheri are not compatable with oscars , any prawn shrimp ,fire eel or dats .
it may work for a while depending on the sizes of all involved , but in the long term this mix is headed for disaster
firstly and most important as ironmunki rightly pointed out , rainbows will not fair well long term kept at full tropical temps , you might get away with it if you keep your tank at the lowest poss temp that the other fish will accept, but most of the time they will die of infection sooner or later , raindows should be kept at uk room temps without a heater in the tank ,as you are in singapore you will probably struggle to get tank down anywhere near what the raindow needs
then we have the size issue , rainbows mostly max out at 7 inches allough can reach 8 inches , there food in the wild includes prawn and shrimp
the oscar will eat anything that fits in its mouth , and they have large mouths and grow much faster than rainbows , same for the fire eel ,the dat depending on the particular fish may prove to be to aggresive for the rainbow who are very peacefull by channa standards and are easly bullied by larger fish
to be honest allough its probably not what you wish to hear , i would return the rainbows , if you really want a snakehead go for one of the medium sized tropical species , obscura or pleuro would be a much better choice for your set up , but all channa would eat the shrimps and prawns
cheers col
