I ask about the size because the rainbow shark and the silver tipped shark...possibly also the pleco are going to be way too big for that tank. if you look stuff up on them online, the silver tipped shark itself gets to almost 2 feet.
your best bet is to look up what fish are good for a 30 gallon tank. and take back your current stock.
i'm sure this isn't what you would like to hear..but unfortunately it's the best bet. my friend thought he could have fish like this in a small tank, but they died a little while after he got them.
also that algae filled water you referred to..unless you mean algae in the tank, it was probably a result of the cycling process, sometimes weird stuff turns up in a tank when there are high levels of toxic ammonia and nitrite in it.
check out the fish species index for some other fish ideas. your tiger barbs would be ok, but you should get a few more i think, but they also can be quite nippy depending on who their tankmates are, so it can be difficult to find other tankmates for them.
good luck