Keep a health log for pea puffers, and keep it per fish. Pea puffers are among the smallest puffers in the world, barely an inch of round body, independently swivelling eyes, and strong personality, and a group tank holds several distinct individuals with different territories, confidence levels, and appetites. A single line saying the puffers are fine will hide the one who is not. Weighing, though, has no role: you cannot meaningfully weigh a fish of this size, and you do not need to, because a pea puffer wears its condition openly in the shape of its belly.
The belly is the scale
Log belly shape in words and simple sketches if they help. After a good feed on snails, bloodworms, or other meaty foods, a healthy pea puffer looks noticeably rounded, almost comically so, and that roundness eases back over the following hours. Before the next feed the belly should look smooth and gently curved, not caved in. The entry that matters most is a belly that stays sunken and pinched even right after the fish has eaten eagerly. A newly bought puffer showing that pattern may have arrived with internal problems, as many are wild-caught, and that is a reason to contact an aquatic veterinarian promptly rather than simply to feed more and recheck in a month.
Record hunting behaviour beside belly shape. A well puffer patrols slowly, eyes scanning independently, and darts at food with real intent. A puffer that watches food, approaches, and turns away, or that has stopped cruising its territory, is telling a different story from one who merely looks full.
Individuals, territories, and feeding fairness
Pea puffers stake out favourite plants and corners, and in a group, bolder fish will guard the best feeding spots. Your log should note who eats where, who has been displaced, and any fish whose fins show nips, because chronic low-level bullying is the commonest reason one puffer thins while its tankmates round out. Note beak condition as well; puffers' teeth grow continuously, and a fish that struggles to bite through snail shell or starts slurping only soft food may need harder foods in the diet and, if eating becomes difficult, veterinary attention for the beak itself.
Water entries belong here too. Pea puffers are fully freshwater fish despite persistent confusion, and they are messy eaters whose hunting leaves debris; pair health notes with water change dates and test results, because a group that goes quiet together is usually reporting the tank, not individual illness.
When the log says act now
Move quickly if a puffer stops eating entirely for more than a day, if the belly sinks despite confirmed feeding over several entries, or if you see laboured breathing, stringy pale waste alongside weight loss in your notes, or a fish resting on the bottom who used to patrol. Take the log to the aquatic veterinarian; for a fish this small, your dated record of appetite, belly shape, and tank events is the substance of the consultation. Do not be tempted to treat on suspicion from the log alone: the notes identify the pattern, and the vet identifies the cause.
A few lines per fish, twice a week, is enough to run this properly. KinsLe's Pet Passport holds each pea puffer's condition and feeding notes together with its records, so every individual's story stays separate and complete.