There are several disadvantages associated with using these mini fish tanks. Since it can only hold small volume of aquarium water, your choice of pet fish is limited to a number of small sized varieties and species such as betta, neon fish, platy and hatchet fish. Maintaining good water quality is somehow difficult in a small enclosure and based on my own experience, it is almost impossible to avoid sudden fluctuation especially in ammonia and nitrate level. I ended up losing several of my platy using these mini fish tank and after that, it taught me a good lesson on never to put in my favorite fish too early before the aquarium water is fully cycled.
One of the techniques I use to set up mini fish tank was to buy a young pleco and put it in together with a bunch of water sprite, which I easily acquired from my favorite local pet shop. As soon as the water is filled about three-quarter almost to the brim, I started running the aquarium filter and at the same time, started applying water conditioner as per the instruction indicated on the label of the bottle. I started releasing my young pleco 2 hours later and then I leave it alone for weeks with periodic water changes in between. The reason why pleco is chosen is because of its hardy nature, which can withstand and tolerate different water chemistry.
I kept to my daily routine to feed the pleco and at the same time conduct regular ammonia and nitrate check using water test kits. Once the the water is fully cycled whereby ammonia and nitrate at the lowest level, I went to scout for a new batch of platy to fill it into the mini fish tank. After that, what follows through are regular care and monitoring to ensure that your pet stays healthy.
Read up more about Tropical Fish Care Guides and learn what are the Common Mistakes made by aquarium owners.