Originally Posted by freshwaterguy4u
Puffers and otto are in the betta tank and the betta is in the snail breeding tank. Ammonia has gone down a bit and I've removed two more rotting snails that the puffers had killed. I'm going to just crush the snails from now on instead having them with the puffers to hunt.
I'm somewhat new to fishkeeping (it has been about a year since I started my new job which included fish care), so I'm still learning (a LOT) from reading everything I can online & in books, along with copious amounts of youtube videos -- so please don't feel guilty about doing research on what I (or anyone) suggests!
When it comes to how many fish will fit in a small tank, please remember that you are looking at two things -- one is how much waste the fish will produce, and the other is how much space a fish will need to swim in and be happy. From what I can suss out, the fish-per-inch thing is mostly to do with how much waste a fish will create. The question of the fish's happiness (or level of stress?) is dependent on the size (and dimensions) of the tank (longer is pretty much ALWAYS better than taller), the set-up of the tank (plants/rocks/hiding spots/broken up lines of sight, etc.), the number & species of tankmates, etc.
So while a well filtered tank (especially one with plants) can definitely handle the bio-load of just a couple small fish, the fish's happiness (i.e. their stress or lack thereof, which will affect their behavior -- like hiding all the time, etc. along with their lifespan) is the concerning part. Obviously this varies wildly by species. From what I've read pea puffers are okay alone in a small tank, as would a single betta. Both of these fish are considered rather aggressive though, so you may be signing up any tank mates to a life of constant harrassment. From what I've read, ottos do best with at least a few pals of the same species (for true "in nature" behavior, 10-15 is suggested -- in a MUCH larger tank of course). Other recommendations for this shy fish are plenty of hiding spots, and easy access to algae, which they prefer to eat off plants. Other than ONE website that claimed 1 otto in a 5 gallon was fine, I've never seen smaller than a 10 gallon recommendation for an otto (up to 4 ottos, 1-2 websites claimed), and most suggest 20 gallon tanks.
As with all things, look at the behavior of your particular fish, because maybe it will work out fine, but you may want to transition some of your species to other tanks. Personally, I'm a fan of using nano tanks primarily as shrimp tanks (bonus: higher numbers are perfectly fine in a shrimp tank -- and they're super entertaining!), though you'll need a well aged tank in order to be successful (I see 6+ months as a minimum recommendation, though I had an okay amount of success starting my shrimp earlier).
In any case, your tank is lovely, and I'm enjoying watching it's evolution -- good luck!