Otto's eat mainly brown algae (diatoms). So if you don't have enough of this type of algae, you will need to feed them algae wafers or zuchinni. They do best in schools, so at least 6 would be a good number for your tank.
I'd say a minimum of three so they can have some company. I've had groups of three in a couple smaller tanks for a long time and they seem to be doing all right. I've also had lone survivors from larger groups do fine for long stretches. However, when I can keep a larger group (6+) they do seem to be out and about more. In both large and small groups they seem to like to be near each other a good bit of the time so I try to make sure they have a couple pals in the tank.What is the recommended minimum number of otto's to keep. I do not think I can get away with six in my 12 gal tank.
They stay small so six would be fine for a 60 gallon tank, especially since you have only two Gouramis in there now. I like the Hikari line of foods, they make a algae wafer... http://www.hikariusa.com/products/tropical/algae_wafers.htmlthanks you two for responding...so what kind of wafer is there something in particular, six of them really that wouldnt over do it