Low maintenance aquatic animals that are small ?

Can anyone recommend any low maintenance aquatic animals ? Basically I was brought some sea monkeys by a friend for my office sadly they have died after 6 weeks but was lovely having them whist they we around . It’s made me realise I like the therapeutic benefits of having something living in my office . Ideally needs to be something small as space is a little limited . Low maintenance as I am often away for 3 day at a time .