Why a Baseline Is a Health Tool, Not a Diary
Most fish health problems announce themselves as a change from normal long before they look like illness — which is useless if normal was never written down. A baseline is a short, plain description of how each tank behaves when everything is fine: how the fish greet food, how the school holds together, where everyone sleeps. Three or four lines per tank, refreshed when stocking changes, is enough. The point is comparison. When something feels off on a tired evening, you are not relying on a vague feeling that the tetras 'seem different'; you have last month's words to hold against tonight's tank.
Feeding Response: the Fastest Signal You Own
Record how each species in the tank comes to food on a good day: who is at the surface before the food lands, who feeds mid-water, who waits for food to sink, and who is always last and needs the current to carry food down. Note the shy ones individually — in many tanks one fish's feeding response is the earliest warning the whole system gives. Write down what 'keen' looks like in this tank, including the normal begging, chasing and squabbling, so enthusiasm is not misread as aggression later. One line per species is plenty; the value is that it exists.
Schooling and Spacing Notes That Mean Something
For schooling fish, note the shape of normal: how tight the school holds at rest, where in the water column it cruises, how it scatters at a shadow and how quickly it regroups. Record the same for territorial tankmates — which rock, corner or plant is whose — and for loners, their usual patrol route or perch. Note the normal use of space from top to bottom, because a school that suddenly hugs the surface or a bottom-dweller that starts hovering mid-water is telling you something about the water, not just the fish. These are the observations an aquatic vet or an experienced shop will ask about first, and 'usual for this tank' is only an answer if you wrote the usual down.
Resting Places and Night Behaviour
Fish rest, and where they rest is remarkably consistent. After lights-out, note who settles where: the corydoras along the front glass, the loaches in the cave, the betta on the broad leaf near the surface. Check once or twice with a dim torch rather than the room light, so you do not record startled behaviour as rest. A fish that changes its sleeping place, or sleeps in the open when it never did, has flagged a change worth investigating the next morning — bullying, water drift or the first shadow of illness. Two lines per tank covers it.
Reviewing Baselines When Something Looks Off
When you suspect a problem, read the baseline before you reach for treatments. Work the three observations in order — feeding response at the next feed, schooling and spacing as the tank settles, resting places after lights-out — and write what differs, in the same plain words the baseline uses. If a fish has stopped eating and the notes show it was always first to the surface, that is a specific, reportable change; if it was always last, you have saved yourself a panic. Update the baseline after any real change — new stock, a rescape, an illness survived — so the comparison stays honest. Keeping those baselines with the rest of each tank's history is the idea behind KinsLe's Pet Passport: the feeding, schooling and resting notes kept in one packet alongside the records, so a change is measured against your own fish's normal — not against a guess.