Internal Parasites

Symptoms

Spotting illness early gives the best chance of a cure, so check your fish daily at feeding time. Gradual weight loss despite eating ('wasting'), a sunken or pinched belly, white stringy faeces, and reduced energy. If you see several of these signs together, act promptly rather than waiting.

Causes

A range of internal worms and protozoa picked up from new fish, live foods or contaminated water that rob the fish of nutrients. In nearly every case the underlying trigger is stress, poor water quality, or the introduction of an infected fish - all of which weaken a fish's natural defences.

Treatment

Treat with an appropriate dewormer (praziquantel for flatworms/tapeworms, levamisole/fenbendazole for roundworms) and metronidazole for protozoa, ideally in food. Improve diet and water quality.

While treating, increase aeration, remove activated carbon from the filter (it absorbs medication), finish the full course even after the fish looks better, and keep the water immaculate with regular changes. Always dose for the tank's true water volume and follow the product instructions.

Prevention

Quarantine new arrivals, source healthy stock, and be cautious with live foods. The golden rules are simple: quarantine every new fish for 2-4 weeks, never overstock or overfeed, avoid sudden temperature or chemistry swings, and do regular partial water changes. A stable, clean, low-stress aquarium prevents the large majority of disease.

FAQ

This information is general guidance, not veterinary advice. Consult an aquatic vet for serious cases.