We list five of the more common fish diseases and problems in aquaponics and discuss both proactive and reactive treatments so you can keep your fish healthy and your plants thriving.
1. Ich (Ichthyophtirius)
This is one of the more common diseases that plagues aquarium owners. Ich is characterized by small white spots appearing on the body of the fish, see the picture above for an example. These spots are each actually encysted parasites (gross!). The way Ich most commonly appears is through transmission from a new fish or piece of equipment that was taken from an infected tank/pond. If not treated, Ich will result in death 100% of the time as the parasites move into the fish's gills and decrease its ability to breath until it dies.
The best way to prevent Ich from spreading to your fish is to have a quarantine tank set up for new fish. Before you introduce these new fish to the rest of them, leave the new fish in the new tank for a few weeks and watch carefully for any signs of Ich. If nothing appears, then you're ready to go -- Ich doesn't lie dormant, it's either eating fish flesh or dead. Additionally, while great water quality won't necessarily save your fish from Ich, it can help slow the spread so you can catch it before it gets out of hand. Yet another reason to monitor your water!
There's a number of ways to treat your fish for Ich. If they can stand being in warmer waters for a period of time (ie not goldfish or Koi), you can use a heat treatment for Ich. This will increase the reproduction cycle of the parasite and you can blast it with a dose of medication. Make sure to remove the carbon filtration system though, as this will remove the medication from the water. Also, seek expert advice before medicating your fish to ensure there will be no adverse effects on your plants. Ich can be cured, but it must be caught early. Advanced stages of Ich are very difficult to treat. If you notice your fish behaving oddly, it's a good idea to catch one and inspect it closely for any tell-tale signs of Ich.
Dropsy is a symptom of a bacterial infection. It is often characterized by a bloating of the belly and raised scales, similar to a pinecone. This happens as fluids fill the visceral cavities of the fish to try and fight off the infection. Usually, it's due to some kind of internal organ failure that opened the fish's defenses to bacteria Often it is not contagious, but in the rarer cases it is caused by a virus, it can affect multiple fish at the same time. Dropsy can occur to many species of fish, but is most common in both Koi and Goldfish variations of ornamental carps.
Because dropsy can have multiple causes, it is difficult to prescribe a specific preventative treatment. Like all fish diseases, the best bet is to keep your water quality, feeding schedule, and feed quality as consistently good as possible.
When you suspect a fish has dropsy, the first step is to isolate it away from the rest of your fish. A salt treatment can be helpful as well as a couple of off-the-shelf treatments like antibiotic food. The sad part about dropsy is that once you detect it, it's likely already too late. Your fish has probably undergone severe internal damage that cannot be treated.
3. Fin Rot
Another bacterial disease, Fin Rot is pretty much what is sounds like, the fins of the fish disintegrate, the bases of the fins look enflamed, and sometimes the edges of the fins turn white. Fin Rot is usually an indication of some stressor in the fish's environment. This could come from moving, overcrowding, or being tanked with aggressive fish that nip at their fins. Such environments weaken the fish's defenses, making them more susceptible to bacterial infection and Fin Rot.
The best methods to prevent Fin Rot are to keep your fish in a healthy, stable environment and limit their exposure to the above stressors as much as possible. Keep track of your pH and water temperature and make sure they remain in a healthy range for your fish.
The first step in treating Fin Rot is addressing the root cause. This involves checking your water quality, observing temperature changes, and observing your fish to see odd behavior and/or fin nipping. Once you have discovered the stressor, remediate it so that Fin Rot will not return when treated. Next, remove any affected fish and place them in a quarantine tank. The reason for doing this is that Fin Rot can be cured with antibiotics, but you never want to introduce such medications directly into your aquaponics system as they will disrupt your bacterial cycles. Finally, purchase and apply off-the-shelf Fin Rot treatments to your infected fish in this separate tank. Monitor their health and follow the instructions on the label closely. You want to choose a drug that is effective against gram negative organisms. A quick google search should help!
4. Nitrate Poisoning
Ok, not quite a disease, but it's a problem! Nitrate poisoning occurs when fish are exposed to slowly increasing nitrate levels overtime. In aquaponics it is a major sign that something is imbalanced. It likely means that you either do not have enough plants to effectively remove the nitrates from your water before recycling into your tank, or that your plants are sick themselves, and are unable to absorb the available nitrates. The symptoms of nitrate poisoning are loss of appetite, listlessness, and fish laying at the bottom of the tank. Another type of nitrate poisoning, known as nitrate shock, occurs when fish are suddenly exposed to a dramatically different level of nitrates. While this is usually because nitrate goes too high, it can also be caused by levels falling too far as well. In aquaponics this would only likely occur when the plants experienced a sudden die-off, perhaps after being exposed to extreme temperatures.
You guessed it; system maintenance. Keep an eye on the key parameters of your system to make sure your nitrogen cycle is operating smoothly and make the necessary tweaks as your plants and fish grow. Also, be very careful to avoid overfeeding. Your best bet is to get an automatic feeder and take human error out of the equation entirely.
First step, test the water for nitrate levels to see how bad things are. If bad, reduce feeding immediately to slow down the nitrogen cycle. Increasing aeration in your fish tank will help the beneficial microbes break things down faster. Finally, make sure your plants are healthy. Perform root checks for any signs of disease and consult an aquaponics expert to ensure your fish to plants ratio is balanced.
5. Oxygen Deprivation
More of a problem than a disease, oxygen deprivation or starvation can be one of the fastest killers for your fish. It occurs when your dissolved oxygen (DO) levels drop below the levels your fish need to breath. Fish have different thresholds for how much DO they need to survive (the Snakehead Fish can gulp air and survive in completely stagnant water!), so knowing the minimum level for your fish is critical. When the DO drops too low, fish will come to the surface of the tank and gulp for air. In the very short term, this is a very stressful situation for your fish and can make them more susceptible to disease. In 10-30 minutes after the short term, it can be fatal.
There's a bunch of them and the best way to treat oxygen starvation is to build your system well and establish enough best practices so that you avoid it entirely. A good system design will seek to keep your DO as high as possible with as few moving parts as possible. This lowers the risk of equipment failure and helps ensure you stay well above that minimum threshold. Additionally, sound system design should account for weather patterns and take actions to your water temperature getting too high or below freezing. Next, keep tabs on your dissolved oxygen. An affordable DO monitor like OsmoBot, is a great tool in this regard and can help you avoid catastrophe. In addition to monitoring, build in a backup aerators that can be turned on remotely, and, if your system is large enough to require this, a backup generator to keep your pumps working should the power go out. Finally, be very wary of overstocking your tank. Every additional fish takes up that much more DO.
Whatever you do, act fast. If the power is out, turn on the generator, get a manual pump, do something. Unless your tanks are very understocked, the amount of time between a key piece of equipment failure and death for your fish can be measured in minutes.