I've only had my Betta, Brucie, for a month - he's the sole occupant of a 10-gallon tank. Last week I added a sponge filter - it's very low flow and shoots a small stream of bubbles out of the top. The air pump I'm using isn't the quietest, and I was worried that the noise & bubbles would stress Brucie out. However, he spends a lot of time in the corner of the tank by the filter! He swims around plenty, but I often see him resting behind the tube or swimming around the sponge it checking it out. (he has other things in his tank too, for hiding/exploration).
Also, the tank and lid are 100% secure and there's no way that a cat could ever get in or knock it over, but one of our cats often sits up on the dresser where Brucie's tank is and looks at him. Usually, he swims right up to the side of his tank and looks back at them (not flaring).
Are these things just characteristics of his unique personality? Should I assume that neither the pump/filter or cats are stressing him out?