Ok so thinking about taking out the five black widow tetra, the three guppies and one angel. With the extra room would a severum be ok? Read that my size of tank is ok for one. See my current stock list above. Thanks
To elaborate on the size point… If a fish does not have enough room to actually swim, then it is unlikely to be a happy and healthy fish. Small tanks do increase the chance of stunting by quite a lot. The amount of room that the fish need depends on the species: for example, a 2" zebra danio can get across a 4-5 ft tank in under 1 second, but a 2"
Betta splendens will easily take 5-30+ seconds to cross the same space, so to have a similar amount of movement, the danio would need a bit more space than a Betta, does that make sense? Also, different species have different territory requirements, and that is another point that needs to be considered.
To get a very rough estimate for medium activity fish such as severums, the adult fish length * 5 is the minimum length of the tank, adult length * 1.5 is the narrowest (front to back) that the tank should be and adult length * 1.5 is the height of the tank. This *very rough* guide is only valid for tanks starting from 3 ft long and 15 inches in both other dimensions. It also does not apply to fast fish like zebra danios and to slow fish like Bettas.
So, based on this guideline (which is not amazing, but better than any other one I've seen), a severum would need a tank that is at the very least 60*18*18 inches in dimensions, which is 150*45*45 cm, which is 305 litres / 67 imperial gallons / 81 US gallons. This is the absolute minimum and I like to see fish have some companions, which is why I recommend a 72*24*24 inch tank for the species.
In other words, you can remove *all* your current fish and the tank will still be too small for the severum because it is too short.