I sometimes count more fish than I actually have, and go, *sighs* counted them wrong again
Sometimes, taking a clear full tank shot picture of your tank helps, just count the blurs on the pic, that may give you idea of how many fish you have. Does not always works but sometimes its perfect
I only count my Clown loaches which is more difficult that you would think even though there are only seven. I try to count my zebra loaches and my three BN catfish but htye are rarely out all at once so I'm mostly wasting my time. The diamond tetras and the rummy-nosed tetras don't get counted as there are fifty of them at least. I don't try to count my Siamses Algae Eater either as counting '0' then '1' would just be an exercise in binary.