Fish illness is very distressing to see and it can be hard to know what is happening, why and how to solve it. This article will lay out the common ailments found in most tanks and ponds, what are the potential causes and how to treat your sick fish.

A lot of fish illness comes from stress as it weakens the immune system, allowing infections and diseases to take hold when normally the fish could fight it off. So its always best to check water quality by doing regular testing to ensure your aquarium or pond has the right parameters before moving on to fish treatments. Ensuring filter is working properly, your water changing regularly and that the fish are not being over fed.

If the water conditions are good and the fish is/ are still showing illness then a course of treatment is probably the right course of action. This can be done in the tank/ pond or in a separate “hospital” tank. Its always worth noting that treatments require any UV sterilisers to be switched off and some treatments will kill invertebrates such as snails and shrimp so isolate ill fish away from the main tank if you wish to do your inverts no harm!

Always read the label for any treatment carefully and be careful with hands and upholstery, a lot of the treatments stain!

Below are common ailments, causes and cures:

FUnGUS

Fungus or “cotton wool disease” is a fairly common occurrence in tropical and cold water environments and is usually the result of stress caused by poor water quality, over stocking or poor nutrition. The stress affects the immune system producing high levels of Cortisol that affects, and damages, the growth of the skin. This allows infections to take hold. It is also worth noting that in colder months and sudden drops in temperature reduce mucus production on outdoor fish which can lead to an increase in fungal issues.

Its always best to get in as early as you can with treating fungal infections as it can quickly spread and kill those affected. After testing you water and doing any water changes/ cleans to make sure everything in your water is ok, there are many treatments that can help but make sure you read the labels! Malachite is a very harsh but effective treatment, how ever it will stain the water and is unsuitable for scale-less fish and invertebrates! Pimafix is a far less harsh aquarium treatment for fungal infections. Salt baths can also be very effective as the salt kills the spores of the fungal infection, which explains the lack of fungal issues in marine aquariums

Did you know that Fungal infections are rarely actually fungus but a form of water mould called Oomycetes which are a closer relation to algae but appear and behave like fungi.

fin ROT

Fin rot can be a bacterial infection which causes a ragged fin or a fungal infection which is more evenly spread with a white edge, or both. The usual problems of poor water quality, bad diet and stress are primary reasons for its occurrence as well as a secondary issue when fishes fins are nipped by tank mates.

If spotted, a water change of 40-50% is advised as well as water tests to make sure the underlying parameters are okay and addressed if needed. Also observe fish interactions in daylight and night time to make sure there is no bullying or fin nipping. NT Labs Anti Ulcer and Finrot is a treatment that is also plant and shrimp safe but will also treat wounds and ulcers, do not leave it as fins that have rotten to the base cannot grow back and remember to remove any carbon media before treating.

White Spot

A very common ailment caused by the protozoan parasite Ichthyophthirius multifiliis which gives it the other common nickname of “Ick”. Usually caused by stress from sudden changes in the water, such as temperature, or through transportation into a new environment. Looking like granules of salt over the body, it can be fatal without treatment. NT Labs Anti White Spot and fungus will treat it but remember the parasite will be present in rotting detritus so regular water changes prevents outbreaks.

Flukes and worms

Flukes: Flukes are scientifically known monogenean and digenean trematodes and are microscopic worms that severely irritate the skin, gills and eyes. They are almost impossible to get rid of completely and tend to multiply and cause visible issues when a fish, or the system itself, is under a lot of stress.

Red, irritated skin and flashing behaviour such as rubbing against rocks or objects in the tank are clinical signs your fish might be experiencing flukes. Treatments such as NT Labs anti fluke and wormer can treat it quickly, however read the label and isolate the fish away from the main tank as treatment will kill inverts.

Worms: There are several types of worm such as the anchor worm (pictured above), internal worms such as tapeworms or marine bristle worms which can harm the carer more than the fish.

The anchor worm victim is easy to spot, white strands protruding from the skin so its fairly easy to quarantine away from the others and the same treatment as flukes can be used but internal worms can be very tricky to diagnose properly.

A fish not gaining weight and thinning could be a sign of internal worms. In this case quarantining the fish for 4 - 6 weeks with good water quality and food to observe the progress, as treating the aquarium with incorrect treatments can do more harm than good and could also aid antibiotic resistance.

GILL ROT

Technically known as Branchiomycosis, gill rot is a fungal infection that starts by affecting the gills and spreading further into the skin, it is very often fatal if not treated. The cause is usually a mix of poor water quality, with lots of decaying matter present, and warm temperatures above 20 degrees Celsius. Regular filter maintenance and removal of rotting debris in your pond/ tank is the best prevention and keeping it cooler if possible. Fungal treatments will help but often come too late, so its best to pay attention to your water quality and your fish’ behaviour

DROPSY

Dropsy (or sometimes known as bloat) is easily identified by the swollen bellies and protruding scales, majorly effecting the liver and kidneys. The belly fills with fluid causing organ damage, kinking of the spine, bulging eyes and a number of other nasty symptoms.

The bacteria that causes it (Aeromonas bacteria) are often found in aquariums but fish tend to be able to fight it off and only immunocompromised fish fall foul. Cleaning your tank and filter regularly, making sure your fish are not overcrowded and prevent swings in temperature or pH are your best preventative measures. Quarantining the fish in a hospital tank and using an anti-bacterial treatment will hopefully turn it around if you do spot fish with signs of Dropsy.

ULCERS

Ulcers are open wounds usually caused by a fish with a weak immune system (generally due to stress because of poor water quality) which is unable to fight off invading pathogens, fungi and bacteria firstly with parasites jumping in second. It’s always best to get on top of the water quality issues first before treating the fish, or else the ulcer will just return.