Find and remove what tore the fins
Clean water heals betta fins, but only after the tearing stops. Run a fingertip over every plastic plant, ornament edge, and piece of hardscape in the tank; anything that would snag delicate fabric will shred a betta's trailing fins as he drapes and squeezes past it. Replace sharp plastic plants with silk or live ones, smooth or remove rough decorations, and check the filter intake, which can pin a resting betta's fins and tear them as he pulls free. A sponge cover or baffle solves that and softens the outflow too.
If the betta shares his tank, watch unobserved for a while. Fin damage that appears overnight in neat bites, in a fish who hides from a particular tankmate, points to nipping rather than decor — and no water routine will heal fins while the nipper keeps access. A peaceful tank of his own may be the actual treatment.
The clean-water routine itself
With the cause gone, recovery is mostly disciplined water keeping. Do small partial changes frequently — little and often beats a weekly upheaval — using dechlorinated water matched closely to the tank temperature, poured in slowly so the current never pushes the betta around. Bettas heal in warm, stable water, so confirm the heater is holding steady rather than swinging between day and night.
Keep filtration gentle and the surface calm enough for him to reach easily, because a betta with damaged fins swims with more effort. Lower the water level slightly if he is struggling to reach the surface to breathe, and keep a soft resting place — a broad leaf or smooth platform near the surface — where he can pause without his fins pressing into gravel.
Feed a varied, good-quality diet in small meals he finishes, because regrowing fin tissue is real construction work for a small body, and uneaten food decaying between plants undoes the clean water you are working to provide. Siphon leftovers during changes rather than letting them settle.
Healthy regrowth versus infection
New fin growth usually appears as a clear or pale edge extending from the torn margin — fragile, almost transparent tissue that gradually takes on colour. The tears should look the same size or smaller each day, and the betta's behaviour should stay normal: exploring, displaying, eating eagerly.
Infection looks different. Edges that turn black, red, fuzzy, or ragged and keep receding mean the damage is advancing rather than healing, sometimes called fin rot when bacteria take hold in the torn tissue. A betta who also goes off his food, clamps his remaining fins, rests listlessly, or develops patches elsewhere needs prompt advice from an aquatic vet or a knowledgeable fish shop. Do not add one product after another on guesswork; worsening edges in clean water are exactly the point where experienced eyes should see the fish or clear photos of him.
Keeping the routine tight until the fins return
Regrowth takes patience, and the daily small change is easy to let slide once the betta looks brighter. Keep the changes, the temperature check, and a quick look at the fin edges on a written list until the new tissue has coloured up and held its length, because a relapse into dirty water mid-repair is how simple tears turn into infections.
That list is easy to share in KinsLe, where Care Teams let you assign the small water changes and daily fin-edge check for the recovering betta to whoever is on duty, with each completed task logged as done.