So I'm a biologist and have recently come across the Walstad aquarium method. Basically requires a bowl, potting soil, aquatic plants, sand and a work light.
I've tested this method using a 4 gallon vase.
The bowl/aquarium cycled in 2 weeks haven't had to do a water
change since. MEANING this can come on any sailing trip.
I've used it to keep a betta and nerite snail. And more recently 10 red cherry shrimp for about a month, which are surprisingly fun to watch and reproduce quickly.
If you're interested PM me and I can walk you through it.