there was a 5" silver shark at the pet shop today and i was wondering if my 4 inch oscars would bother it

no but they will compete for space and one will eventually kill the other IMO

ok so if i am planning on getting rid of these fish before size becomes a problem will they be right

Do you mean Bala Sharks? A 40 gallon is too small for even an Oscar, so think about upgrading to at least a 75 gallon for a single Oscar.

Edit: To keep two full grown Oscars you are going to need at least a 125 gallon tank.

yep, and if your talking bout an iridecent shark they need a 125g tank too

Only problem with iridescent and bala sharks is the fact they are schooling fish. Not only does a single one need a large tank, 6 of them certainly do. Bala sharks can grow to over a foot in length. They are also quick swimmers so you need a considerably large tank to house them. I do recommend getting a larger tank for your oscars. I think they will be fine in the 40 for about 6 months if you keep up with the water changes. From what I have seen, you can have a full grown oscar in a year.

Post some more pics of your oscars! They are one of my favorite fish. If I ever get a bigger tank, 150+ gallons, I'm definitely going to get a couple of them.

less then 6 months`

You'd get away with two Oscars in 75gals as adults if you cant manage a 125. It's not the optimum size and of course bigger would be better but based on the most common tanksize recommendations out there the rule general followed is 55gals as a minimum for one oscar/ 75gal for two.

So much for my plans to start a tiger oscar out in a 10g and upgrade to a 29g in december, then get a 55 summer after this... oh well. :blink:

it'll help a bit becasue its a breeder, but yeah greab a nicce 75 or 90. feeding them earthworms will speed up the growth.

i plan on trading them in at the petshop when they get too big for my tank so earthworms will be out of the diet