Can I add any more fish

[16gallontanker]

I went ahead and took all my corys out of my tank and left the super red bristle nose pleco in and my female Betta and 3 otos in should I keep 5 sterbai corys and add them back in or would my tank be overstocked then Ior should I add a different fish like a top feeder instead I really want to hear y'all's opinions on this since the tank is only 20 gallon standard size.

 

[jaylach]

There is an OLD rule of thumb that comes fairly close when stocking. Look up the mature size of all fish. In a 20 gallon tank the total inches of fish should not exceed 20 inches. The old rule is one inch of fish per gallon of water.

 

[GaryE]

I have a personal rule for stocking - if I ask myself if I have enough room, I don't. If I know I have space, then I proceed, but asking the question, especially asking other people, is the answer. I've been on forums and fish talk for a number of years (since the internet had no images) and I don't think I've ever seen anyone ask if they had space where I thought the answer was "yes". You already know. You just want to hear something different, if you're like the rest of us.

That's frustrating because we like fish and want more of them to watch. The 1 inch per gallon rule was a pet shop formula to sell more fish, and we hobbyists jumped all over it because we liked it. It gave us overstocking with a rule to support it. It works for slender bodied fish like neons or zebra danios, popular fish when it was invented. It works less well when fish are also wide and tall - how many inches are there in those fish?

Your Ancistrus will grow, and as a herbivore, it will be a waste producer. It's going to be in constant competition for food with the 3 Otocinclus. That's a larger issue than traditional stocking. You should only have one fish with specialized needs (diet/territory/group numbers) per tank, in something as small as a 20 gallon.

Personally, I'd keep the sterbai and rehome the Otos. The Betta will own the surface and open water, the sterbai would own the bottom reaches and the Ancistrus (or the Otos) would have the glass and decor as their spots.

 

[TwoTankAmin]

While stocking has to be concerned with tank size, fish size and parameter needs, there is another consideration which we often forget. That is how will the various fish we put into to tank together get along. A lot of health issues with fish are related to stress levels. Fish which will be harassing each other or attacking each other make tank life pretty stressful for some or all of the inhabitants.

Since stress opens a fish to disease, and diseases do not often respect species differences, it makes sense to insure our selection of fish is one which considers compatibility.