Goldfish on its side 90% of the time

Question
I have a 70 gallon tank (approx). We have a turtle, a snail, two
sucker fish, (4) approx 4 inch gold fish and (1) 5 to 5.5 inch gold
fish in this tank. The big one constantly lays on his side eats on his
side and swims on his side and he lays on the bottom a lot and
looks like he's dead but he has been this way for like 3 weeks. What
is going on with this fish and is this something I can treat

Answer
Hi Flo,

That sounds like a very nice setup you have =).  Good job.
But let's get to your fish.  Sometimes fish do this naturaly, which can be a bit confusing, but most of the time, it is because your fish has SBD (swim bladder disorder).  This is caused by either not enough or too much oxygen in their swim bladder (this controls their depth in the water).  The fish will unintentionaly float, sink and sometimes wobble.  To cure this, you need to fast him for 2-3 days and then feed him boiled, skinned, mashed peas.  Please mash them even if he is big enough to eat them whole as it is better for his jaw. Once again, very nice setup, send me a pic sometime, I would appreciate it =).

I hope I helped,
James