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Keeping fish should be an enjoyable and rewarding experience and knowing what signs to look out for is key for healthy and happy pets!

Fish are less obvious than other animals when they are unwell and often subtle changes in their behaviour can signal something is wrong. A lot of fish diseases are difficult to see without close inspection but most conditions and diseases bring about a change in behaviour.

What is normal fish behaviour?

What to look out for: - A happy, healthy fish is usually one who swims at a normal pace, is alert to its surroundings and reacts quickly when food is introduced. Fish who rest listlessly, perhaps on their sides, fins clamped together and do not respond to food are obvious clues something is not right. Feeding time is therefore a great time to observe any abnormal behaviour.

What is not normal fish behaviour?

Erratic behaviours, such as sudden bursts of stop/start swimming, jumping and ‘flashing’ - where fish scrape the sides of their bodies against a surface, could indicate parasites. Hanging near the surface of the pond with the appearance of gasping for air could be low oxygen levels or potentially gill damage or infection.

Water Chemistry & Testing

The first thing to do if you notice something isn’t right is to test the pond water. Correct water chemistry is fundamental to a healthy environment and will often be the lead cause of disease in a pond.

In an idillic world, fish keepers would routinely test their water at least once a week. Recording the test results in a table or graph would also help quantify any changes to the water over time. In reality, this is not often what happens, and as fish keepers we mainly only test the water as a reaction to noticing something unusual. All too often the results come back with less than ideal parameters and then an action is taken to rectify the situation. Regular testing would help prevent these fluctuations in water conditions - and therefore avoid many cases of sick fish.

The most important parameters to test for are: ammonia, nitrite, nitrate (the three parameters of the nitrogen cycle), pH, KH & GH (acidity and hardness of the water). The NT Labs Pondlab - 200 Multi-test includes tests for all 6 of these in one conveniently packaged, detailed kit.

When starting a new pond the key parameters to test for are ammonia and nitrite. These will be present during maturation of the pond and pose a threat to the health of the fish even in low concentrations. Pond filtration removes these toxins from the water by culturing bacteria that converts ammonia and nitrite into the less harmful nitrate. Nitrate levels will increase over time and should be monitored to prevent algae blooms. If ammonia or nitrite are present, perform a partial water change and supplement the filter with a bacterial supplement (NT Labs Pond - Live Filter Bacteria) to rapidly reduce the toxicity of the water. Review the amount of fish food being added to the pond and consider withholding food for a short period too.

Mature ponds should contain no ammonia or nitrite but the ageing process will create acidic conditions over time. The acidification process will decrease carbonate hardness (KH) and subsequently lead to an unstable pH so it is important to test regularly to prevent levels from dropping too low. Pond fish prefer a pH of between 7 and 8, a KH of at least 6 dKH and a GH of at about 8 dGH. Hardness levels of those stated create a ‘buffer’ to stabilise the pH, if these get too low this can cause rapid swings in pH which kills fish quickly. Water changes are again key to maintaining good water chemistry. Fresh tap water replenishes lost minerals in aged pond water which will keep the water at a stable pH value. Always remember to treat new tap water with a dechlorinator (NT Labs Pond - Tap Water Chlorine Remover (Mature). This will remove harmful chlorines, chloramines and heavy metals. If the KH or GH are too low and fresh tap water does not bring them up to recommended levels, buffering agents should be added for long term stabilisation (NT Labs Koi Care - GH Minerals Up & Koi Care - KH Buffer Up.)

Water quality can have a detrimental effect on the fish both directly and indirectly. It can lower a fish’s immune system which makes the animal more prone to infectious diseases. Some water parameters are poisonous if left to get to the extremes. High nitrite, for example, will affect the fish’s ability to absorb oxygen in to its blood. This can result in the symptoms of not enough oxygen present in the water (fish gasping at the surface) even though the oxygen levels are fine.

Disease Diagnosis

Disease diagnosis is important to determine the best course of action once water quality has been assessed. Fish diseases can be broadly categorised into either bacterial, fungal or parasitic diseases. Viral diseases can also occur, such as carp pox, but these are usually rare and harder to treat if an outbreak occurs.

Bacterial infection symptoms: The most common bacterial infections in pond fish are ulcers, fin rot, tail rot, mouth rot, dropsy and popeye. Mouth rot is often confused with a fungal disease due its white cotton wool like appearance. Dropsy is the late stage diagnosis of an internal bacterial infection whilst popeye and red patches on the body are also signs of a bacterial infection. Ulcers can often get a secondary fungal infection if left untreated but should still be treated with an anti-bacterial first.

Bacterial infection treatment: NT Labs Pond - Anti-Ulcer, Fin-Rot & Flukes (Bacterad) & NT Labs Koi Care - Acriflavin. The latter is the pure active ingredient whereas the pond treatment also contains 2 other compounds. NT Labs Pond Salt Plus can also beneficial during treatment to help ulcer wounds heal, reduce stress and support the fish osmotically.

Fungal infection symptoms: White cotton-wool like growths on the body or fins of the fish, often a secondary infection of an open wound (e.g. ulcer).

Parasite infection symptoms: Sugar-grain sized white spots along the body or fins of the fish, flashing, jumping, gasping at the surface, mucous-like appearance on the body. Larger parasites include flukes, lice and leeches.

Some parasite infections can only be observed under a microscope (e.g. Trichodina, Costia) whereas white spot (Ichthyophthirius or “ich”) is easier to see on the body. Flashing and jumping from the water is a fish’s reaction to the irritation caused by the parasite attaching themselves to the body.

Fungal & Parasite infection treatments: These 2 different disease categories are often treated together as their treatment chemicals can be used together if dosed correctly. NT Labs Koi Care - FMG Mixture and Pond - Anti-Parasite & Fungus (Eradick) use the same 2 active ingredients: malachite green and formaldehyde. F-M-G has a higher dose of formalin and is therefore only suitable for koi. NT Labs Anti Parasite & Fungus is suitable for all species of pond fish if used correctly. Both are very effective at treating a broad range of parasite and fungal infections.

Other parasitic infections, such as flukes, lice or anchor worm, require different treatments: NT Labs Koi Care - Argusol & Koi Care - Flukasol. Both are very effective treatments but confirm which parasite the fish have before use. NT Labs Koi Care - Permanganate Dip can also be used as a dip treatment against all parasites including lice, leeches & anchor worm.

Treating a Pond

There are a number of important considerations to bear in mind when treating a pond. It may seem obvious, but the most important thing when using medicine around a pond is to always thoroughly read the label before adding to the water! Here are other precautions one should consider before adding any treatments:

  1. Not all fish species can tolerate some of the active ingredients used to make pond treatments and this is usually noted on the packaging. Note that if a treatment is labelled for koi, this should be taken as suitable for koi only and not assume it is safe for all. These koi treatments are usually stronger and are designed for ponds containing koi only.
  2. Test the pond water before treating - some treatments can have a negative impact if the water chemistry isn’t right before treating. Always make sure ammonia and nitrite levels are at 0, pH is between 7-8 and KH is at least 3-4 dKH (unless using a product to solve an issue relating to one of these parameters.)
  3. Correct dosage - it is important to first have a rough idea of how many gallons the pond holds. Whilst some treatments aren’t harmful if overdosed, others are lethal if not given the correct amount. A rough guide of length x width x depth (in feet) multiplied by 6.25 will give imp. gallons. Times this by 4.54 to get litres. Every treatment has a certain tolerance built in, so don’t panic if an extra millilitre or two is dosed. If you are ever concerned about dosing your pond, be sure to use the NT Labs Dosage Calculator.
  4. Never mix treatments unless they say they can be on the label. NT Labs Koi Care - Malachite and Koi Care - Formaldehyde are an exception, but most treatments shouldn’t be used simultaneously. Always leave at least 7 days between switching treatments to make sure there are no cross reactions.
  5. Always treat the pond leaving plenty of time to observe the fish in case they react negatively to the treatment.
  6. Turning the UV off during treatment is important as UV light can degrade the medication. It is usually advised to leave the UV light off for 10 days during treatment.
  7. Maintain excellent oxygen levels. Treatments can reduce dissolved oxygen in the water so it’s important to make sure all pumps, waterfalls and filters are running at their optimum to maximise water movement and maintain high oxygen concentrations. This should be maintained 24/7 during the course of the treatment.
  8. Safe temperature range - most treatments have reduced efficacy below 10°C and many have a maximum safe temperature of between 25-30°C. High temperatures reduce water’s ability to hold oxygen. Couple this with adding a medicine and this could cause a sudden extreme drop in oxygen levels.

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