What ageing actually changes
A firemouth cichlid can live well past a decade, and old age arrives as a slowing rather than a stopping. The scarlet throat that flared at rivals fades, patrols of his territory get shorter, and he spends long stretches resting near the bottom or behind his chosen structure. He may still flare at a reflection, just less often and with less conviction. None of that is illness by itself - it is a fish budgeting energy. Senior care is about removing the small taxes on that budget: current he must fight, food he must chase, and tankmates who still treat every day as a contest.
Take the effort out of his territory
Firemouths earn their living sifting mouthfuls of substrate, and an old fish keeps doing it if the substrate lets him. Fine sand rather than coarse, sharp gravel lets him sift without wearing at his mouth and gills, so deepen a sandy patch in the part of the tank he has claimed. Ease the filter outflow so his resting corner sits in gentle water, and make sure a cave or rock stack gives him a station out of the main flow. If younger, pushier fish have been added over the years, a rearranged boundary or a simple divider can return his corner to him without moving anyone out.
Food delivered, not contested
The most practical change is at feeding time. An old firemouth is easily out-raced, so drop sinking pellets or a defrosted portion directly into his territory, ideally while the faster fish are busy with food at the far end of the tank. Feed a little less overall than in his prime - an ageing metabolism lays down fat more readily - but watch that his belly stays gently rounded rather than pinched. Going off food entirely is different from eating slowly: a senior who ignores offered food for several days running is telling you something has changed beyond age.
Water quality is the senior support system
There is no tonic for an old fish, but there is water quality, and it matters more each year. Ageing kidneys and gills cope less well with nitrate creep and skipped maintenance, so keep changes regular and modest rather than heroic and rare, and test often enough to catch a rising trend rather than a crisis. Stable warmth in his usual range, a filter that is cleaned in rotation so its bacteria survive, and no sudden rescapes - an old fish's world should change as little as possible while everything in it stays clean.
Know his threshold for outside help
Most senior firemouths simply need the gentler regime above, but some signs go past ageing and deserve a vet who treats fish, or an experienced aquatic health professional: rapid breathing that does not settle, sores or fuzzy patches, a swollen or hollow belly that changes over days, or the several-day food refusal described earlier. What helps that conversation enormously is a timeline - when the appetite dipped, when the resting increased, what the water read at the time. Keeping those dated observations in his Pet Passport on KinsLe means the history is written down as it happens, not reconstructed from memory on a worrying day.