Welcome to OFL and the world of the Oscar. Unfortunately, a lot of these places don't know what the hell were talking about. Don't worry, you'll get nothing but good advice on this website;)

no need to go anywhere else if I do say so myself
Okay, the best bit of advice I can give it the moment is to keep a very close eye on your water. I expect your Oscar is fairly small at the moment, even so, it will still produce a lot of waste for its size. It's good that you are getting new tanks in, 20 gallons is definitely too small. Just remember that 55 gallons is only big enough for one Oscars don't be tempted to get another one. If it is possible to get a bigger tank, then do. If not, you'll just have to make do with the one Oscar. Anyway, he'll keep you amused all on his own.
Have you got some water testing kits? Also, did you cycle the tank before putting the fish in? If the answer to these two questions is no, get yourself a kit quickly and do a small water change every day. Also, if you are not cycled, don't be tempted to feed too much. Although babies do need to be fed quite a bit, you can't afford to introduce it to poor water conditions at such an early age. Don't be afraid to ask any questions, however trivial they may seem