Guppy fins can look rough for two very different reasons: physical damage (nipping, sharp decor, strong flow) or true fin rot (a bacterial breakdown usually linked to stress and water quality). The fix depends on which one you’re dealing with, so the first step is diagnosing correctly.
What fin damage looks like
- Clean tears or splits: edges look sharp, like a rip in fabric.
- Damage appears quickly: “fine yesterday, torn today” often points to nipping or decor.
- One fish gets hit most: a single target can mean bullying or dominance behaviour.
What fin rot looks like
- Fraying with uneven, melting edges rather than clean splits.
- Progression over days: the tail slowly shortens or looks ragged.
- Inflamed base: sometimes a whitish edge or redness near the tear line.
Step 1: test water before you treat
Regardless of cause, test ammonia and nitrite first. If either is above 0, do a 30–50% water change and increase aeration. Many “fin rot” cases stop progressing once water is stable and clean.
Fixing physical damage
- Remove the cause: identify fin nippers, sharp plastic plants, rough rocks, or strong current.
- Improve cover: plants and hardscape reduce line-of-sight chasing.
- Keep water pristine: consistent changes help fins regrow cleanly.
Fixing fin rot (when it’s real)
If fraying continues despite clean water and calm tank conditions, treat more directly:
- Increase maintenance temporarily: smaller, more frequent water changes for 7–10 days.
- Reduce stress: stable temperature, gentle flow, no major rescapes.
- Consider medication: only if progression continues. Use a targeted antibacterial per label, and keep oxygen high.
Recovery expectations
Fins usually regrow, but regrowth can be slower than people expect. The edge often starts clear/transparent and colours back up over time. If the cause remains (nipping, ammonia spikes), fins will keep degrading.
The simplest rule: clean water stops most fin problems. Once the environment is stable, you can decide if the fish needs treatment or just time to heal.
