diffrence in sex

Question
how can you tell the diffrence in the sex of an oscar? I have four of them, I just added the last two not even a month ago and my very first pair i bought is tearring them apart. I keep putting other oscars in, but those two keep terrozing them. I did what the pet store told me to do, which was always buy in a pair, and never bigger or smaller then the others, to stay very close in size. Well, ummm would i be able to tell if there is too many males or females or even which is which???? lol please help...

THANKS

How big is your tank? 150 gal
What type of fish? Oscar
How many fish do you have?4 + 1 pleco
Type of filter? under gravel and powerheads
What are the pH, ammonia, nitrite levels? no ideal
How often do you change water?once every 3 months
How many gallons of water are replaced every time? approx. 50


Answer
Hi Katie;

The original oscars are just defending their territory. They are very aggressive fellas and it's just what they do. Move the decorations around to keep them from feeling like it's their own space and they may settle down a bit. Add more rocks and caves too so the weaker ones can hide when necessary. Don't pile larger rocks too high though. It could break the glass if they fall when the fish move things around.

You really can't tell the sex of oscars. Some breeders can tell the sex of their own breeding stock, but that's usually because they watched them spawn and could see their genital papillae as it was protruding. Otherwise, it's just not possible to know.

Oscars are very messy guys and must have a water change and gravel vacuuming once a week, every week. Replace 25% every week and your fish should be happy and healthy. If you don't have one already, get a "spill-free" water changing system. It siphons, vacuums and refills too. So easy to use, especially for big tanks like yours.

You have a serious problem in your current setup for the future I'm afraid. Oscars are too large and messy for an undergravel filter. Their wastes plug it up and their constant digging and pushing tubes loose renders it useless. It will get much worse as they get big enough to pop the power heads off the tops. You need a power filter or canister filter for them. I know it's hard, but you really should get the undergravel plates out of there. I'm speaking from experience here and it will be a mess in the long run.

Good luck...

At Your Service;
Chris Robbins