An elderly angelfish should be checked over at home once a week, but the weighing part of that question deserves care: angelfish are tall, thin and built around long, delicate fins, and an old fish pays more for handling than a young one. For a senior angelfish, the regular check is visual and thorough, while weighing is an occasional event done gently and only when the number will change a decision.
The weekly visual check for an elderly angelfish
Once a week, give the senior angelfish a slow, deliberate inspection while he hovers in his usual spot. Look along his profile for body depth: an ageing angelfish who is losing condition shows a sharpening ridge along the back and a head that looks larger against a thinning body. Check the trailing edges of the long ventral and anal fins for fraying or splits, because old fin tissue heals slowly and early damage is where infection starts.
When weighing an elderly angelfish is worth doing
Weigh an elderly angelfish only when a trend number will actually be used: when he looks thinner across two weekly checks, when a veterinarian asks for it, or as part of a calm health review every few months. Never weigh to a weekly schedule the way you might a land pet, because each weighing costs this species a netting, a lift and a fright, and an old fish's stress recovery is slow. If the visual checks show a steady shape, steady appetite and steady swimming, skip the scale entirely; the absence of change is the finding. When you do weigh, make it count by photographing him in profile the same day, so shape and number are recorded together and the next comparison is honest.
How to weigh a tall senior angelfish safely
Weigh a senior angelfish in water, never in air. Float a smooth container in the tank, tare a scale with the container and its tank water, then guide the fish in with a soft, fine net or by herding him gently into the submerged container, lifting water and fish together so his fins are never folded against a dry surface. Keep his long fins fully supported by water at every moment, work in dim light, and have the tank lid ready so a startled senior cannot jump. Note the weight immediately and return him within a minute or two, watching that he rights himself and resumes hovering normally.
What to record at each elderly angelfish check
A useful senior record pairs the weekly observations with the occasional weight. Note appetite in plain terms, fin condition, any new spots or thickening around the head and lateral line, and how much time he spends resting versus patrolling. Angelfish can live long lives, and an elderly individual's baseline is personal: the fish who always rested after meals should not be flagged for it, while the lifelong patroller who suddenly sits still should be. Compare each week against his own recent pattern rather than against angelfish in general.
Changes in an elderly angelfish that need a vet
Contact an aquatic veterinarian if an elderly angelfish loses visible body depth across a few weeks despite eating, develops pits or sores around the head, or stops feeding for more than a day. Laboured breathing, a persistent tilt he cannot correct, or fins that erode quickly rather than fray slowly also move the case beyond home checking. Bring the weight record, the weekly notes and recent water results; for a fish who cannot be examined like a mammal, that paper trail is the examination. KinsLe Pet Passport keeps an elderly angelfish's weights, check notes and water records in one packet, ready to hand over at any vet visit.