When you set up an Oscar tank you should consider a choice of three substrates for the bottom. Gravel, gravel or gravel. The reason why you should use gravel is because Oscars love to dig around in it actually its programmed into them because its part of their breeding habits. those that have bred Oscars who have reared their own fry will have seen them dig pits in the gravel and then move the fry into the pits and often cover the fry with the gravel.They may even move them from one pit to another. In the wild this would keep the fry safe from predators. The very first pair of Oscars that i saw was in a friends house. He showed me the fry in the gravel. I couldn't see them and humored him thinking that he was seeing things. Sure enough a couple of days later he phoned me to say that the fry were free swimming and i went round to see my first pair of Oscars with fry swimming round them. Luckily i have now seen it many times from some of the Oscars that i have owned and each time they have done exactly the same thing with the fry in the gravel. Oscars need gravel. If you have a bare bottom tank they will have nothing to move around. If you put sand in there and they dig around 1. it will create a lot of sand moving around in the water and 2. Sand could irritate their gill plate. On top of that if they do spawn it would be difficult to hide the fry.I'm sure that there are going to be people out there that have spawned Oscars with sand or bare bottoms but,in my opinion gravel substrate is the only one to use and it should be around 3 inches deep.

Wow 3 inches. I have a gravel bottom of about 1 inch. I used to have 2 inch worth but I was told that too much gravel is a haven for bacteria so I removed half of it. I am not planning breeding my oscars so is 1 inch ok?


In fact, what can I do to discourage my oscars from breeding when they get big enough. My biggest oscars are about 10 inches including tails?

i don't think there is anything to do to discourage them form spawning, i know they put bromide in the tea in prison but don't think that would be wise for the fish. As for the depth if they are ok with an inch then leave it but three inches does give them more to dig around in. As for the bacteria i do agree that if the gravel was in there for a long time it could have some spots but seeing as Oscars dig around in it i don't see it a s a problem. Its possible that anaerobic filtration can take place in the gravel as the water flows much more slowly through the gravel which has much less oxygen available. This is ideal breeding territory for the type of bacteria needed for anaerobic filtration. This type of bacteria feed on nitrates and so will lower the level of nitrates in a tank. My set ups always have lots of gravel and they have never suffered form rising nitrate levels.But if it ain't broke don't fix it