The swim bladder is a simple yet complex organ that is absolutely vital to the wellbeing of our Koi. As the name suggests it is basically a gas filled bag – but what they do and how they work is still pretty remarkable, and an understanding of the mechanisms involved helps in understanding how they can go wrong and what to do about it.
In the August issue (issue 5) of Koi Talk we catch up with Dr Adrian Love to discuss this fascinating organ… but if you can’t wait for your magazine to land in your letterbox here’s a snippet of the article!
Swim bladders are hard-working organs; they are constantly adjusting to achieve neutral buoyancy in the fish, so anything that impedes this ability is going to cause significant and profound issues. Unfortunately, there are many things that can cause problems.
Typically, something impedes the movement of gas between the front and back portions or, more importantly, along the pneumatic duct. So the fish will swim lopsidedly because half of its bladder is puffed up inside and it can’t release the air. Sometimes the cause of this blockage will be a physical deformity getting in the way – unfortunately too often seen amongst ‘fancy’ goldfish varieties that have been bred to be a shape aesthetically pleasing to the owner but deformed and twisted inside. This is often exacerbated when the gut has wrapped itself around the swim bladder which, if the gut is full of partially eaten food, can restrict the regulation of gas. Incidentally, if there is build-up of gas within the gut itself (caused by taking in excessive air at the surface when feeding or a more serious bacterial infection in the gut) then it can produce symptoms of swim bladder issues – an x-ray is typically the only way of confirming this.
But back to genetics. Koi are rather predisposed to internal tumours (called neoplasia), which as they grow can squeeze the internal organs around the swim bladder and restrict the free passage of air. In such cases, the symptoms develop slowly – over months/years and can be confirmed by an uneven silhouette of the fish. Unfortunately, surgery is the only solution. More dramatically, a physical trauma can knock/damage internal organs so they get in the way and have the same effect though the symptoms will develop immediately and there won’t be the irregular swelling.
Sometimes, an internal bacterial infection will cause inflammation of the pneumatic duct or the swim bladder itself. This can be associated with a build-up of fluid within the chamber of the swim bladder which, of course, reduces the buoyancy.
Such cases are very difficult to diagnose but are often seen in fish with systemic bacterial infections in which case they will be generally in poor condition and probably not feeding. There are videos available of people inserting needles and syringes into the flank of Koi, hoping to hit the swim bladder in order to aspirate – to clear or inflate it. However, this will – of course – result in puncturing the swim bladder or other nearby organs and blood vessels. It can easily to lead to much greater issues. In any case it should only be undertaken by a vet who will typically use ultrasound to guide the needle. A course of antibiotics may treat the infection.
Water quality has a huge effect on all aspects of the internal workings of the fish and poor water quality (particularly elevated ammonia, nitrite and nitrates) can cause organ failure, including the swim bladder.
As a short term relief for fish with swim bladder issues, it is commonly suggested to put them in a warm, dark, shallow bath of water containing salt or Epsom salts (3g per L for long terms baths). This makes sense: the warmth will help the immune system of Koi (if there is a bacterial issue), dark because they will be stressed if they are restricted to bright water, shallow because the fish with buoyancy issues will feel more comfortable where these issues are not so evident, salts will help support the fish (because the water is slightly denser) and act as a general tonic, and Epsom salts will relive constipation of there is an issue of blocked food trapping air.
Look out for the full article in issue 5 of the magazine. If there’s a particular topic that you’d like to know more about why not drop us an email at firstname.lastname@example.org and we’ll consider it for a future issue of the magazine.