Hamster toys: a different twist
Petville makes a few different hamster toys. This toy train and the bridge (not shown here) are perfect in aquariums. They have no rough edges, are easy to clean and most importantly, allow the fish ample room to escape to the surface.
I have the train in Baby Blue's 5 gallon tank. She has no companions (she's anti-social to the max) and not too much decor, as her eyesight was compromised from a popeye infection.
I have seen BB inside the train, which is like a hamster tunnel section with the 'roof' removed. At any time, she can rise to the surface. There is nothing blocking her vertical assent.
Just another betta-worthy toy to consider! :D