CichlidFish.com - Fish That Think.

First, please forgive me for asking what has probably been covered a million times here. I seem to be having computer issues and could not do a search. It just sits and never pulls anything up. I tried on two different browsers too So, again I am sorry for not being able to look for this info on my own.

I have 2 Oscars who are about a year old. The live with a plecostomus. They used to live with 2 other fish that they had been with from day one and never had an issues. Anyhow, they started digging in the gravel and uncovered a large area of the underground filter. Then they killed the 2 other fish Now she has laid eggs and he is being very mean to her. They both want to guard the nest and are bickering. It looks like the male is winning and she keeps hiding/pouting in the corner. Now I noticed that they both have some small scuffs/cuts on them. Very small, but I am worried it will get worse. Is this normal, its it ok?

They live in an 80 gallon Aquarium. Money is tight, so buying a new one is probably out of the question. I do have a "kid" tank that isn't set up. Its about 20 gallons, maybe.

I am just so worried, I don't want dead Oscars. Can anyone help me and or post links to some info for me?

Thanks!!!
Rainy

Well Oscars dig, and they dig to nest as well. As for killing off the tankmates, that happens sometimes when they breed.They also can do that because they feel the other fish are in their territory. Now as for the nest care, again this is typical behaviour in some case's.
Are the eggs white or beige?
Did you actually see who laid the eggs?
Keep and eye on the tank ammonia, and nitrite and nitrate levels. UGFs are not a good choice at the best of times, IMO, and with gravel digging fish, not a good choice at all.

The UGF is one of two filters and I use it with 2 powerheads. I also have a dual bio wheel. If I offer them some flat large rocks, would that help with the problem of the eggs ending up in the slats of the UGF? I guess only the fish know that. Why do you feel that the filter is bad? I want to do what is best for these guys.

I did not see who laid the eggs. BUT, one of the fish has a bull shaped head. He looks like his head has a hump on it. The girl has a smooth head that is much more streamline. He is in general bulkier and huskier looking. She is more dainty and of a totally different shape. I am assuming that I have the sexes correct, but you know what they say about assuming! Am I wrong?

The ammonia, and nitrite and nitrate levels are bad. I asked at a local store and was told that it was probably because the dead tank mates were not removed in time. (We were away and a friend was feeding them. She didn't notice that they had been killed. One was behind decorations and the other had been *sigh* mostly eaten.) So now I am desperately trying to get the water back in check.

Oh, and they are no longer fighting, I shooed him away from her a few times and he laid off. She went back to fanning the eggs and then started to pick through them and eat them. By this morning they were all gone. And they were white. I assume she knew they were bad and thats why she ate them. Would that be correct?

Sexing of Oscars is difficult, body shapes and sizes have no real relavance with them. Wild males have caudal spots (eye spots) on their backs, under the dorsal fin. Wild females only have the one on their tail. From "domestic" Oscars, venting is about the only sure way to sex them.
Since the eggs were white, they were not sterilized.
You could have a male and a female, or two females. The eggs may not have been fertalized by the male, lots of possibilities.
As for the UGF. They use the gravel to house the nitrifying bacteria.
Since the Oscars dig, this disturbs that system, that is just one of several reason for not using UGFs. I am glad you have biowheels,
but you really need some filtering for the mess the Oscars make.
If you don't run a hob, or a canister filter, your really loading up the waste in the gravel, which will lead to problems with ammonia, etc. It may well be that, and not just the two dead fish, that is causing the spikes. Personally I would not trust a fish store that didn't advise against using a UGF for a cichlid tank.
There was a very good thread on UGFs here, I will see if I can find it, and link it for you.

Ok here it is.
http://www.cichlidfish.com/portal/forums/showthread.php?s=&threadid=15749&perpage=10&pagenumber=1

ONLY way to sex oscars correctly is to vent them! body shape, head shape, etc. differ from fish to fish even in same brood. You could very possibly have 2 girls! UGF bad for oscars becase they dig and when part of GF is uncovered it doesn't function properly.