Free tool · triage, not a diagnosis
Is my fish okay?
Something looks off and you want a calm, honest read. Pick what you're worried about, tick what you're seeing, and we'll suggest possible causes and safe first steps — always leading with the water. This never diagnoses and never gives a medication or dose; when something needs a vet, it says so.
1 · What are you worried about?
2 · Tick what you're seeing
🐟 fish — start here
- Test the water FIRST — ammonia and nitrite should both read 0, and nitrate should be low (well under 50 ppm). A hidden water problem is behind the large majority of fish illness and mimics almost every disease.
- If ammonia or nitrite is above 0, do a water change now — that alone is often the whole fix, and it means the tank is not (or no longer) fully cycled.
- Check the temperature is correct and STABLE for your fish (tropical fish need a heater). A chill or a swing stresses fish and invites disease.
- Improve conditions: add gentle surface agitation for oxygen, stop overfeeding, and remove any uneaten food or a dead fish.
- Don't reach for medication first. Watch calmly, get the water right, and if a fish is clearly ill, move it to a quarantine/hospital tank rather than dosing the whole display.
- A swollen belly with scales sticking out like a pinecone (a possible sign of dropsy — serious internal illness; very hard to treat once the pinecone look appears)
- Several fish sick or dying at once, or sudden unexplained deaths
- Not eating for several days with visible weight loss / a pinched, hollow belly
- Open sores or ulcers, or a fuzzy cotton-wool growth spreading over the body
- Laboured breathing or gasping at the surface that a water change and aeration don't fix
- Anything serious or persistent despite good water quality — this is when a fish-savvy or exotics/aquatic vet is the right call (more vets treat fish than people expect).
Common signs
White spots like grains of salt or sugar
Possible causes: Ich / white spot — a very common parasite that shows as tiny white grains on the body and fins; It typically takes hold after stress, a temperature drop, or a newly introduced fish.
Safe first step: Get the water pristine and the temperature warm and stable first — ich thrives on stress and cold. Test the water and do a water change if anything is off. Ich is treatable with a clear plan, but stabilising conditions and quarantining new/affected fish comes first. See our sick-fish guide before doing anything else, and treat with a clear reason, not blindly.
A couple of spots that vanish and never return may just be stress; spots that multiply, or come with scratching and fast breathing, are the concern.
Scratching or "flashing" against rocks, plants or the substrate
Possible causes: Skin or gill irritation from poor water quality or high ammonia (the most common reason); The early stage of an external parasite (ich, flukes) before spots appear.
Safe first step: Test the water first (ammonia/nitrite should be 0) and do a water change if anything is off — irritation from bad water is the usual cause. Then watch closely for white spots or other signs, and get a quarantine plan ready in case a parasite is starting.
Ragged, receding, or "melting" fins
Possible causes: Fin rot — a bacterial problem that is almost always secondary to poor water quality, stress, or an injury; Fin-nipping from an aggressive tankmate.
Safe first step: The first-line "treatment" is the water: test it and do a series of water changes to get it pristine and stable — mild fin rot often heals on its own once conditions improve. Rule out a fin-nipping tankmate. Bettas are especially prone in poor or cold water. Only more severe, spreading cases need more, and that's a moment to ask a fish-savvy vet — never a random medication.
Cotton-wool tufts or a fuzzy grey/white growth
Possible causes: A fungal or bacterial infection, usually secondary to poor water quality, an injury, or stress; Sometimes an excess slime-coat response to an irritant in the water.
Safe first step: Get the water pristine and stable first — many mild cases improve once conditions are right and the wound/irritant is removed. If it spreads or the fish declines, move it to a quarantine tank and get a fish-savvy or aquatic vet's advice rather than dosing the whole display.
Not eating
Possible causes: Stress from a recent move, a new tank, or a water-quality problem; The wrong food, or a shy/finicky new fish still settling in; The early sign of illness when it comes with other signs.
Safe first step: Test the water and give a new arrival quiet time and cover. Offer a small variety of good foods (many fish are tempted by frozen/live foods). A day or two off food is common; a week-plus with weight loss is the worry — watch for other signs below.
Rapid or laboured breathing, or gasping at the surface
Possible causes: Low oxygen, or a temperature that is too high; An ammonia or nitrite spike burning the gills; A gill parasite or irritation.
Safe first step: Add gentle surface agitation/aeration and test the water NOW — an ammonia/nitrite spike is a common cause and a water change is the fix. If the water is warm, cool the tank gradually. If gasping continues despite clean, oxygenated water, get experienced help.
Labyrinth fish like bettas and gouramis do gulp air at the surface normally — the concern is fast, laboured breathing plus other signs.
Clamped fins, hiding, dark/faded colour, or lethargy
Possible causes: Stress — a new tank, a chill, aggression from a tankmate, or a water problem; The general early "feeling unwell" sign for almost anything.
Safe first step: Test the water and check the temperature is right and stable. Watch for bullying and provide cover/plants. Persistent clamping with other signs (spots, not eating) means look harder and prepare a quarantine tank.
Floating, sinking, or swimming tilted / upside-down
Possible causes: A swim-bladder / buoyancy problem, often linked to diet (gulping air with floating pellets, or constipation from overfeeding); Water quality, or in fancy goldfish the round body shape makes this common.
Safe first step: Check the water first. Try switching to soaked/sinking foods and a day or two off food — buoyancy issues from diet often ease. This is especially common (and often manageable) in fancy goldfish. If it persists or comes with other signs, ask a fish-savvy vet.
Stringy white feces, or a pinched, hollow belly
Possible causes: An internal parasite or gut problem (more common in wild-caught fish); Not enough of the right food, or the fish is being out-competed at feeding time.
Safe first step: Offer varied, quality foods and make sure this fish is actually getting to eat. Persistent white stringy feces with weight loss warrants moving the fish to a quarantine tank for closer observation and advice from a fish-savvy vet — not a blind medication.
Swollen body with scales sticking out like a pinecone
Possible causes: This "pinecone" look is a classic sign of dropsy — fluid build-up from serious internal (often organ) failure, usually in a fish already weakened by poor conditions.
Safe first step: This is serious and hard to treat once the pinecone look appears. Move the fish to a clean, stable quarantine tank to keep the water pristine and reduce stress, and seek a fish-savvy or aquatic vet's advice — this is a point where professional help is genuinely worth it.
Prevention is the real lever: stable, pristine water and low stress keep fish strong enough to resist the underlying causes.
Several fish sick or dying at once
Possible causes: A water-quality crash, an ammonia/nitrite spike (a new or over-stocked tank), or low oxygen; A fast-moving disease, or a toxin (a chemical, an aerosol, a contaminated hand or object in the tank).
Safe first step: Treat this as an emergency. Add aeration, test the water, and do a large water change with dechlorinated, temperature-matched water. Check for anything that could have contaminated the tank. Get experienced help quickly — and a vet if it continues.
🦐 shrimp or snail — start here
- Test the water — ammonia and nitrite at 0, nitrate low. Shrimp and snails are even more sensitive to water quality (and to swings) than most fish.
- Check there is enough GH (general hardness) and a steady, not-too-low temperature — shrimp and snails need minerals in the water to build and moult their shells.
- Confirm nothing copper-based went into the tank. Copper (in many fish medications and some plant fertilisers) is highly toxic to shrimp and snails — if it did, do a water change and run fresh carbon.
- Remember a clear, empty shrimp "shell" is usually a MOULT, not a death — shrimp shed their exoskeleton and hide while the new one hardens. Look for the animal nearby.
- Acclimate new arrivals slowly (drip if you can) — most invert losses trace to a too-fast change in water on arrival.
- A shrimp or snail died shortly after any medication or additive went in (suspect copper — water change and run carbon)
- Several shrimp/snails dying at once (check water quality, copper, temperature and oxygen)
- A shrimp stuck part-way out of a moult ("white ring of death") — often a hardness/mineral or water-quality issue worth correcting for the rest of the group
- A snail sealed up, floating, or not moving for days with a foul smell (it may have died and could foul the water — remove it)
Common signs
A shrimp/snail died after a medication or additive went in
Possible causes: Copper or another invert-toxic ingredient — many fish medications and some plant fertilisers contain copper, which shrimp and snails have very little tolerance for.
Safe first step: Do a water change and run fresh activated carbon to pull the compound out, then test the water. In future, never dose copper-based products in a tank with shrimp or snails — treat sick fish in a separate quarantine tank instead.
A clear empty "shell" — or a shrimp stuck in its moult
Possible causes: Usually a MOULT — shrimp shed a clear, hollow exoskeleton and hide while the new one hardens (this is normal and healthy); A genuinely stuck or failed moult can point to a hardness/mineral or water-quality issue.
Safe first step: Look for the animal hiding nearby — a clear, hollow shell means a healthy moult, not a death, so leave the shed to be eaten (it recycles minerals). If a shrimp is truly stuck mid-moult (a "white ring" between body and tail), check that GH and water quality are right for the whole group — it's usually a husbandry fix, not a rescue.
A shrimp/snail sluggish, not moving, or a snail sealed up
Possible causes: A water-quality problem, or a temperature/hardness that's too low or unstable; A too-fast acclimation on arrival (shock); Snails do rest or seal up for a while, and rest naturally — give it time before assuming the worst.
Safe first step: Test the water and check temperature and GH are steady and in range. Gently right a stranded snail near a surface it can grip. New shrimp/snails must be acclimated slowly — most losses trace to a rushed acclimation. If a snail stays sealed and starts to smell, it may have died and should be removed before it fouls the water.
Several shrimp or snails dying at once
Possible causes: A water-quality crash, an ammonia/nitrite spike, or a sudden parameter swing; Copper or another toxic additive in the tank; Not enough GH/minerals over time.
Safe first step: Test the water immediately and do a water change with dechlorinated, matched water. Check that nothing copper-based went in, and that GH and temperature are stable. Shrimp and snails are your tank's "canary" — a colony crash usually means something in the water needs fixing for everything living in it.
Quick answers
Does this tool diagnose my fish?
No — and it never names a medication or a dose. It suggests possible causes and safe first steps for the signs you tick, always leads with a water test, and tells you when to get a fish-savvy or aquatic vet involved. It can't see your tank; a vet can.
My fish looks sick — what is the very first thing to do?
Test the water: ammonia, nitrite, nitrate and temperature. The large majority of sudden fish illness traces to a water-quality problem, and a water change to fix it is often the whole treatment. Reaching for medication before checking the water treats a symptom while the cause keeps working.
My fish has white spots — is it ich?
Tiny white grains like salt on the body and fins are most often ich (white spot), which takes hold after stress or a temperature drop. It is treatable, but stabilise the warm, clean water and quarantine new or affected fish first, and treat with a clear plan — not blindly. See our sick-fish guide before acting.
What does a bloated fish with sticking-out scales mean?
A swollen body with scales raised like a pinecone is a classic sign of dropsy — serious internal illness, usually in a fish already weakened by poor conditions. It is very hard to treat once the pinecone look appears, and it is a point where a fish-savvy or aquatic vet's advice is genuinely worth seeking.
My shrimp looks dead — is it?
Probably not. A clear, hollow "shell" is usually a healthy moult, not a death — shrimp shed their exoskeleton and hide while the new one hardens. Look for the animal nearby, and leave the shed to be eaten (it recycles minerals).
When should I see a vet?
We triage, not diagnose. See a fish-savvy or exotics/aquatic vet when a fish is seriously ill (e.g. dropsy), when problems persist despite good water quality, when several fish are affected, or before using stronger medications. More vets treat fish than people expect.
Go deeper: Sick or dying fish — what to do · Is this normal behaviour? · The nitrogen cycle · Interpret your test results