I just dont know :(

Question
Hello, i have 2 oscars which kind i couldn't tell you ...only place to get fish in my town is wal-mart (horrible) and they are numbskulls .....i picked the oscars because i knew they got large and i have them in a 55 gal tank .Wal-Mart advised to feed them feeder fish or dried krill but after about 2 weeks one of my oscars became very dull and lifeless. With a little research i found out it was probably my feeders and stopped giving them goldfish. Now i feed them Dried krill (main food) Tetra cichlid sticks (On occasion it seems to brighten there colors) and as i was feeder goldfish again (but its  been a few months and i keep then in a controlled tank for at least a week to insure at least decent health) NOW for what i dont know .........anything.
ive been reading around alot trying to find information abuot how my tank is supposed to be kept and i don't really find specifics for Oscars always Oscars-Cichlid's...Are they very different? Is it bad to just assume my water is safe?
Suggested pH levels and what does the nitrate level (etc) in my tank actually effect.........I do about 20% water changes at LEAST every 2 weeks my filter probably moves anywhere between 100-200 gallons of water an hr and i vacuum the rocks just as frequently....should i make any changes or additions to my upkeep or my food? and is there any other basic information you have for me. (Sorry i know you said you do Cichlid's but like i said everywhere i go it talks about both)

Answer
Hi Steven,
 Oscars are cichlids.  Cichlids are a large family of freshwater fish and oscars are one kind of cichlid (there are over 2000 other cichlids in the world).  It sounds like you are doing a good job with the oscars.  Don't use the feeder fish -- they carry too many diseases that will eventually get into your oscars and kill them, which is very sad.
Crickets would be a much better choice as a treat in addition to the Tetra cichlid sticks and the krill.

 It is not bad to just assume that your water is safe. In my opinion, many people spend too much time and money testing their water whereas the best thing you can do for a fish is do the regular water changes.  20% once every two weeks is okay, but once a week would be much better particularly as the oscars get larger and produce more waste.  

-- Ron
  rcoleman@cichlidresearch.com
  Cichlid Research Home Page <http://cichlidresearch.com>