Join Date: Feb 2011
Location: Currently based in NJ
In my experience, plants do a lot better when there's a filter. A heater's also pretty much needed... just because of the Thai fish.
Basic rule of thumb is an inch per gallon... unless the females you're getting are King bettas, they generally get around 2" long and most people frown upon any more fish.
In my opinion, if you really want to add some others with the bettas, a plecostomus is a great algae eater as they don't need to be in groups and don't grow any larger than an inch. (Snails might be a little too slow to keep up with a ten gallon.
I've got three Glass Catfish with my five girls. They're mostly nocturnal fish and hang out in their cave while the bettas are frolicking around... and they eat almost any food that sinks (though algae wafers aren't great nutrition for them of course). I use flakes, others get frozen mysis shrimp. Anyway, I love these invisible fish as they're rather curious, and they make an interesting group to have.
Other fish that are compatable with bettas and the water conditions they need should be fine, though don't go overboard, of course. Always be sure you're doing enough water changes with more fish... The plants will definitely help, but I believe with more than five fish in the ten gallon, a 25-50% water change should work for every week.
Test your water to know how often you need to do it; each tank is different as conditions vary on location, type of water, pH, etc.
Weekly water changes have kept conditions right for mine.