A goldfish cannot be lifted out for inspection, so a weekly screen works by watching carefully in a set order. Three parts, done the same way each week at feeding time, build the comparison that makes a slow change visible. Dim room lights reflecting on the glass can hide detail, so view the tank with the aquarium light on and the fish swimming freely rather than netted or cornered.
First Part: Gills and Breathing
Watch the gill covers as the fish breathes. Healthy movement is even and unhurried, with both covers opening and closing in a smooth rhythm. You may glimpse the red gill tissue at the edge of the cover as it opens, and a rich red colour there is what you want to see. Note anything different. Covers that flare outward, movement that looks rapid or laboured, one side working harder than the other, or a fish hanging at the surface taking in air all count as changes. Look along the cover edges for pale patches, excess slime, or spots. Breathing changes often appear before other signs, so this first part earns its place at the front of the screen.
Second Part: Fins and Tail
Move your eyes to the fins once breathing has your attention. A healthy goldfish holds its fins spread and whole, with the tail flowing rather than clamped tight against the body. Check each fin in turn: tail, dorsal fin along the back, the paired fins underneath, and the fins behind the gills. Look for splits running with the fin rays, red streaks, white spots or patches, blackened edges, and margins that look thinned or ragged compared with last week. Clamped fins held close for a whole observation, rather than a moment, belong in your notes as a behaviour change even when the fins themselves look intact.
Third Part: Body, Scales, and Shape
Finish by scanning the whole body from both sides as the fish turns. Scales should lie flat and smooth, giving an even outline. Note any lump, raised or pinecone-like scales, sore or reddened patch, fuzzy-looking area, or a change in the body's outline such as a swollen side or a slimmer profile than last week. Watch swimming during this part as well. A goldfish that lists to one side, struggles to hold position, or rests on the gravel between efforts is showing you something the scale check alone would miss. Note appetite at the feeding that opens the screen, since a fish that ignores food it usually takes eagerly adds weight to anything else you found.
Writing the One-Line Record
Close the screen by writing a single dated line covering all three parts, even when the line reads normal throughout. That unbroken run of normal weeks is the baseline that gives a future change its meaning. When something does differ, expand the note with where on the body you saw it, which side, and a phone photograph through the glass if the fish cooperates. Test the water during the same session whenever you find a change, because water quality sits behind many goldfish problems and your vet or aquatic shop will ask for those figures first.
When a Screen Finding Needs Advice
Seek advice from an aquatic vet or a knowledgeable aquatic retailer promptly if breathing looks laboured, the fish stops eating, fins deteriorate between weekly screens, or raised scales appear. Rapid changes in fish move faster than a weekly rhythm, so a worrying finding midweek justifies an extra look rather than waiting for the scheduled screen. Avoid adding treatments to the water on guesswork, since an unneeded product can harm the filter bacteria the tank depends on, and a clear description of what changed, paired with water test figures, gets you better guidance than a treated tank does.
Those weekly screen lines accumulate into a health diary inside KinsLe's Pet Passport, where gill, fin, and body notes sit alongside water-change records and any advice you were given, ready for the next consultation.