Start With Who Is Actually in the Bag
Clown killifish are usually sold as pairs or trios rather than as anonymous groups, so the paperwork should say exactly what you bought: how many fish, and how the seller sexed them. The banded males carry the showy, flame-like tail that gives the species its clown name, while females are rounder and plainer, and a receipt that just says killifish leaves you guessing later when you are trying to explain a missing female or an extra male. Have the scientific name written alongside the common one as well, since several small Epiplatys species look alike as juveniles and are easily mixed up in shop tanks.
Captive-Bred or Wild, and Why It Changes the First Month
Ask for the origin in writing. Captive-bred clown killifish are generally steadier on prepared foods and accustomed to aquarium water, while wild fish from slow, leaf-stained West African waters can be more delicate, more inclined to jump, and more dependent on live food at first. The record should also say how long the fish were held before sale and whether they were feeding confidently at the surface. A fish that has only just arrived and has not yet eaten in the shop is a different purchase from one held for weeks, and your paperwork should make that distinction visible rather than leaving it to memory.
Soft, Acidic Water Values Belong on Paper
More than most small fish, this species needs its seller water documented. Clown killifish thrive in very soft, acidic water, often well below neutral pH, kept warm but not hot. If your home water is harder and more alkaline, an abrupt transfer can shock them, so get the holding tank's pH, hardness, and temperature noted on the receipt or care sheet. Then you can plan a slow drip acclimation and decide honestly whether your supply water suits them long term, or whether you will be preparing softened water for every change. That written starting point also explains later behaviour: a fish sulking after a water change can be checked against the values it came from.
A Surface Feeder's Menu, in Writing
Record what the fish have been eating, item by item. Clown killifish hunt almost entirely at the surface, taking tiny insects and larvae, and many individuals will ignore food that sinks past them. If the seller has them taking fruit flies, small live foods, or finely crushed floating items, write that down, along with anything refused. Note too whether the fish were fed in a quiet tank, because shy killifish in a busy shop system may have been outcompeted and arrived thinner than they look in a quick glance. Your first job at home is matching that menu before experimenting.
Your Own Notes Complete the File
Once home, log the tank they entered, the lid arrangement you are using, since this species is a determined jumper that finds filter cut-outs, your first pH and temperature readings, and the day each fish first fed at the surface. Photograph each male's tail pattern, which helps you tell individuals apart in a trio. If a fish stops rising to feed, darkens, or spends its time hidden at the bottom, those observations, set against the seller's water record, give an aquatic veterinarian something concrete to work from. Keeping the receipt, sex mix, origin, water values, and menu together in KinsLe's Pet Passport turns scattered shop notes into one tidy killifish packet you can consult at every water change.