I have a 55 gal. tank with one Oscar 9 inches and a second that is 7 inches. They are both about a year and a half old. I recently found out the tank is too small for the both of them and would like to use them as a breeding pair if they're male and female, which I believe they are. I took a water sample into my LFS and it tested fine. The larger of the two which I think is the male has been spitting rocks into piles. I first am wondering what this means and second would like to know how to test the water myself. I am also wondering if I should do a water change even though the larger Oscar is doing all this work changing the tank around. Thanks for any help you can give me and this is a wonderful website.

water changes can initiate spawning,so do a water change if neccasery.as for doing the tests yrself,go to yr LFS and buy a good testing kit trust me this is the most important tool you could hv.my personal opinion is look 4 the most expensive testing kit u can find as the cheap kits are not very accurate.

It sounds like your Oscars are getting ready to spawn you may be able to help them along with lots of live food(earthworms, river shrimps, meal worms and insects from the garden) and a water change which lowers the temperature of your tank around 4 degrees as this will mimic the rainy season in the wild. Personally i wouldn't worry about the water quality if the conditions weren't right your |Oscars wouldn't be getting ready to spawn. That said it can take a while for the Oscars to spawn and patience is a virtue where spawning is concerned. When i breed a new pair of Oscars i always remove the eggs from the pair just to make sure i have a successful pair of Oscars. Good luck.

Alright, I've been keeping up on water changes and feeding them live food and now the larger of the two will not allow my hand in the tank at all when doing water changes. Neither one of them have ever been aggressive toward me in a year and a half. I don't see any eggs although the larger of the two wont let any thing over a certain area and wont leave that area except to chase the smaller one off or my hand when doing (attempting) a water change. Would it act like that with no eggs yet? Why would it chase the other one off?

from my experiance with my two the male always gets agressive have a good look at what hes near to see if theres any eggs. if i remember correctly the male tends to protect the eggs till they hatch.ide say put somthing smooth in for them to lay there eggs on as they preffer it to the bottom of the tank. ive had two batches but few get fertelized and always get eatin within two days
good luck with yours and keep us updated

cheers drew

It is not unusual for one Oscar to chase the other away from a spawning site although in my experience this normally leads to the Oscar eating the eggs as it sees the other one as a threat. You don't say if you have gravel in the tank and this is one thing that is essential for breeding Oscars. Once the fry have hatched,the Oscars will move them to a pit dug in the gravel and will then cover them in in the gravel. Once this happens it is extremely hard to see the fry. This is one reason why i don't recommend sand as a substrate. Oscars will normally lay on a flat surface and i use a piece of slate. All that said it may be that you have two females and one is driving the other away from the intended spawning site (females will spawn without a male present) the only sure way you will know is if the spawning tubes are down on each fish. The male tube is pointed like a pencil and the females tube is more rounded and larger.

My Oscars have been showing breeding behaviours for about 2 months now and no sign of eggs as far as I can tell.

They constantly dig a hole in the sand to the bottom of the tank and guard it for a couple of days sometimes and then they cover the hole up. This is repeated almost every day and they are both aggressive to each other until one gives in then they just sit there next to each other over the spot.

I am still not sure if they are a male and female. I have never seen organs protruding as far as I am aware. Is this behaviour sometimes shown between two males or two females?

both male and female o's will dig and show signs of courtship. at sexual maturity (about 12-14 months) you should see the first batch of eggs arriving (Assuming you actually ahve a female) and if you have a mature male the fry will follow in about 3 days. im not sure if two males will go through the mating ritual but i beleive that 2 females will. only when you see the breeding tubes or fry will you know if you have a mating pair