i have a 75 gallon tank and at the moment have 2 tiger oscars, 2common oscars and 1 albino oscar all are about 2-3 inches long. Is this to many ? all are healty and the water is clear i have a tetratac 1200 filter. I am fairly new to fish keeping and would welcome any advise.

for happy fish keeping, you can keep two oscars in that
tank until they reach to 10 inches long. beyond that, you
need to upgrade.

5 oscar of 2 to 3 inches long would be overstock. you are inviting
trouble

And boy do they grow fast upto the 10"!

if you plan on keeping the oscar in a 75 gallon tank for life then the answer to your question is one.
if you would like to keep 2 oscars for life then you will need a tank in the 100-125 gallon range. along with this you will need adequate filtration to go with the tank size you choose.