Each breaker control certain outlets inside your house, 15-20amp is alot, mine was 10-15amp and I replaced it with 20amp.
15-20amp is how much power, pump, lights all the power wattage add up to amp. With my 2 x 250w, 3 x 175w, pumps, 1/2HP chiller..etc it add up to like 15 + amp
So you should find which breaker control the your tank, if it's 20 then change to 25 or it's 15 then go with 20.
Don't jump from 15 to 30 or from 20 to 40 this is very dangerous.
HD have it for like 10-15 dollar, buy a same breaker like the one you have at home. Turn the breaker off, un-screw one side w/ wire at a time ( don't touch both wires ) just one wire at a time. Once you get both wire connected / screw to thenew breaker, push it back in place. Turn the break back on.
You don't have to change the wire since you only upgrade the breaker from 15 to 20 or 20-30, your old wire should be good.
Or you can run your electric cords to a different breaker. Run a extension cord to a different outlet from a differnt breaker, then you don't have any more problem.
Lets say chiller can run from a different outlet, lights from a different outlet. In this case you are using more than 1 breaker to share the power. DONT PLUG everything into 1 outlet.