Read this first
This article assumes you have already done the diagnostic work: tested the water, ruled out ammonia, oxygen and temperature shock, and confirmed that what you are seeing is actually a disease. If you have not — stop and do that first: Why Are My Fish Dying? Most "sick" fish in this country are poisoned or suffocating, and medicine does nothing for either. If the main symptom is fish hanging at the surface breathing hard, start here instead: Why are my fish gasping at the surface?
Still here? Then three rules before any treatment:
- Identify before you medicate. The three common diseases need different treatments, and the wrong one wastes the week in which the right one would have worked.
- Know what your medication kills besides the disease. Several common treatments are copper-based — lethal to shrimp and snails — and some damage the filter bacteria, which turns a sick-fish problem into a poisoned-tank problem. Read the label for the words "invertebrate safe" before anything goes in the water. (Why copper matters.)
- Fix the stressor too. Disease organisms are present in most tanks most of the time. Healthy fish resist them; stressed fish do not. If you treat the disease and leave the stressor — a temperature swing, bad water, bullying — it comes back.
Disease 1: Ich (white spot)
What it looks like: distinct white dots, like grains of salt sprinkled over the body and fins. Fish flick and rub against objects ("flashing"), clamp fins, breathe faster as it spreads to the gills.
What it actually is: a parasite with a multi-stage life cycle — and this is the key to killing it. The white spot on the fish is armoured; no treatment touches it. The parasite is only vulnerable in its free-swimming stage, after it drops off the fish and before it finds a new host.
Why you got it: in this country, overwhelmingly two causes — new fish added without quarantine, or a temperature swing (the AC-vent problem, a cold water change, a failed heater). Ich is the classic aftermath of a chilled tank: the placement guide.
Treatment:
- Raise the temperature gradually to 28–29 °C over a day. This does not kill the parasite — it accelerates its life cycle, forcing it into the vulnerable free-swimming stage faster.
- Increase aeration first. Warmer water holds less oxygen, and ich on the gills is already costing the fish breathing capacity. In a UAE summer the tank may already be at 29 °C — in which case skip the heat step entirely and rely on the medication; do not push past 30.
- Dose an ich treatment for the full course — typically 10–14 days, which covers the complete life cycle. Malachite-green-based treatments work; check shrimp safety. Stopping when the spots disappear is the classic failure — the spots falling off is the parasite reproducing, not dying. Treat to the end.
- Vacuum the substrate every few days during treatment — the reproductive cysts sit in the gravel.
On salt: salt at 2–3 g/L can support this, but it will not clear ich on its own — the encysted stages are out of its reach and the tank reinfects itself. What salt actually does, and at what dose.
Disease 2: Fin rot
What it looks like: fin edges turn ragged, milky-white or blackened, and recede progressively — as if the fin is dissolving from the edge inward. In advanced cases it reaches the fin base and the body.
What it actually is: a bacterial infection — and here is the important part — almost always an opportunistic one. The bacteria are in every tank. They win when the fish's immune system is suppressed, and the suppressor is nearly always chronic: sustained poor water quality, nipping tankmates, or long-term stress.
Which means: fin rot is a symptom of the tank more than of the fish. It is the disease equivalent of a warning light.
Treatment:
- Water first. Test everything, then a 30–40% water change, then another in two days. Early fin rot very often reverses with clean, stable water alone — no medication.
- Find the stressor. Check nitrate (chronic elevation is the classic cause), check for a fin-nipper (compatibility), check the temperature stability.
- Medicate only if it progresses despite clean water — an antibacterial for fin rot, full course. If only one fish is affected and you have a quarantine tank, treat it there: the display tank's filter and invertebrates stay out of the blast radius.
- Regrowth looks clear or pale — new fin tissue is transparent at first. That is healing, not spreading.
Disease 3: Fungus (and the disease that pretends to be it)
What it looks like: white or grey cottony, fluffy tufts — like mould — on the body, mouth or fins. Distinct from ich's discrete salt-grain dots.
What it actually is: a true fungus that colonises damaged tissue — a wound, a scrape from rough handling, tissue already hit by another infection. Healthy intact skin resists it; fungus is nearly always a secondary problem.
The lookalike to know: columnaris ("mouth fungus") is actually a bacterial infection that produces similar cottony patches, typically around the mouth, and moves much faster. If the "fungus" is spreading in days, especially mouth-first, treat it as bacterial, not fungal — an antifungal will do nothing.
Treatment:
- Find the original injury or stressor — rough décor, an aggressive tankmate, poor handling, or another disease underneath.
- Antifungal treatment for true fungus, full course. For suspected columnaris, an antibacterial — and act fast; it does not wait.
- Clean water throughout — fungus thrives on organic waste. A tank with fungus problems is usually a tank with a maintenance debt: the weekly rhythm.
The quarantine tank: the upgrade that changes everything
A bare 20–40 litre tank with a sponge filter and a heater, kept in a cupboard until needed, does two jobs:
- New arrivals wait there two weeks before touching your display tank — which is how you stop importing ich in the first place. Every disease in this article most commonly arrives on a new fish.
- Sick fish get treated there — full-strength medication, no collateral damage to the filter colony, the shrimp, or the plants. Copper-based and harsh treatments become usable again.
It is the single cheapest piece of insurance in the hobby, and the difference between "one sick fish" and "a medicated display tank."
What not to do
| Don't | Because |
|---|---|
| Dose a "general tonic" at the first sign of anything | Wrong-target medication stresses the fish, and several damage the filter or kill invertebrates. Identify first. |
| Stop ich treatment when the spots vanish | The visible spots are the armoured stage. Vanishing spots mean the parasite is reproducing in your gravel. Full course, always. |
| Use copper-based medication in a tank with shrimp or snails | It kills them, reliably. Treat in quarantine instead. |
| Combine multiple medications | Interactions are real, oxygen demand climbs, and several combinations are lethal at normal doses. |
| Treat fin rot with antibiotics while ignoring the nitrate | The bacteria are the symptom. The water is the disease. It will return. |
| Forget the carbon | Activated carbon in the filter removes medication as you dose it. Take it out during treatment, put it back after to clear the residue. |
The UAE angle, in one paragraph
Two local patterns worth knowing. First, summer tanks run warm already — the classic "heat treatment" for ich may be redundant or even risky when the tank is at 29 °C in August; lean on the medication and the aeration instead. Second, temperature swings here come from the AC, not the weather — a tank in a vent's airflow gets chilled repeatedly, and recurring ich in an otherwise healthy tank is very often a placement problem wearing a disease costume. Fix the location and the "recurring disease" stops recurring.
Common questions
Can I treat ich with heat alone, no medication? At 30 °C+ the parasite struggles to reproduce, and heat-only treatment can work — but it is slower, oxygen-hungry in a climate already short of it, and risky for cool-water fish. Medication plus moderate heat is the reliable path.
Do I need to treat the whole tank or just the sick fish? Ich: the whole tank — the parasite is in the water and gravel, not just on the fish. Fin rot and fungus on a single fish: quarantine and treat individually if you can.
My fish has spots AND ragged fins AND sits on the bottom. Which disease? Probably none — that combination is classic ammonia burn. Back to the diagnostic, test first.
Is salt a substitute for medication? For nitrite protection, yes — that is its best-evidenced use. For the three diseases on this page, no. The dose chart and what it treats.
How do I stop this happening again? Quarantine every new fish for two weeks. Keep the temperature stable (placement!). Keep nitrate low with the weekly rhythm. Those three habits prevent almost everything on this page.