Fish tank

Arthur wants to have pets for years. This year, thanks to the pandemic, we have time and have a good reason to finally get him a fish tank with 8 black skirt tetra and 9 cardinal tetra. Tetra fish needs to be in a group of 6 or more. It depends on the species but 6 is generally an absolute minimum. Our fish tank is only 29 galan which can support "29 inches" of fish. One black skirt adult is ~2 inch and one caridnal is about 1 inch. So this is the most we can get. We started with 6 black skirts because black skirts are relatively low maintenance. Four weeks later, we added 2 more black skirts and 8 cardinals. This is way too aggressive and we lost 5 tetra fish in 4 days. Learning it in a hard way, we added bacteria, changed water more often (daily) for a couple of weeks, and then slowly increases the time between water change. We monitored the water quality daily. And finally, we get a stabilized tank and only need to change water biweekly. The fish are healty. We added a few more cardinals later and ended with 8 black skirts and 9 cardinals.