Well their was this oscar at about 3-4in and wanted to know if I can put in in a 16 gal tank with a red tail botia. The reason why it so small is because I divided my 60 gal tank and have a 16 gal part for my red tail botia which may or will eat my small comunity fish. So is it okay to have an oscar with that condiation in a small tank? Reason being is because I will get my 100 gal tank within 2-3weeks.

If it is only temporary quarters until you get a 100gal it should be fine for a few weeks. However I wouldn't recommend putting it in with the loach. You should keep new fish quarantined for 4 to 6 weeks before introducing them with other fish. I wouldn't take the chance of introducing something to any of my existing fish if I was you.

Why do I have to do that? What does that do? How come I have to do that?

When you bring in new fish you never know if they are carrying something that may transmit to your healthy fish. Especially if it comes from a pet store. Even if the fish looks healthy it may still have a disease. It is just a good idea so you don't infect your stock of healthy fish and/or a healthy tank.

Ic so how would I set one up?

Just like any other tank....could even be just a bin with filter heater etc.

Ic thanks but lets say Im putting new fish in a tank. What should I do first?

Well, acclimate them accordingly to what your putting in. In a QT tank you can pretty much just put them in as long as temps and PH are close to one another. Lighting should be the same as other tanks, on at least 8 hours a day...feed them as you normally feed other fish and do plenty of water changes to keep water pristine. Make sure to use a established filter or if using a new filter put some gravel from an established tank or a filter pad from an established filter in to seed the tank with good bacteria. This way you wont have to worry much about cycling.

...and get a test kit

The Oscar will eventually get large enough to make a snack of the loach.

I see. I was wondering lets saw I have my 100gal tank set up and already have 2 oscar and wanted to add 4 jds who are small abou an inch would they be okay or should I put a divider till their big enough? Also how many fish do you guys think can I put in my 100gal tank? Because I was thinking of putting 2 oscar,4 jds,2 jaguars, and maybe a flowerhorn or arowana.

I understand your point. But lets assume that I will get a larger tank when they get bigger maybe a 200gal tank. Would that be okay? Because what Im thinking is if it would be okay since their just babies? Because at the lps the oscar are about 3 inches and the jds about 1-2inches.