Maintaining the Health of Your Koi

When you built your pond, you probably spent a lot of time planning its design. You made sure every plumbing piece was in place. You carefully selected your filter and your pump. Everything seems perfect. While everything mechanical is in place, did you know that you need to plan your fish just as carefully as everything else?

Many experienced fish keepers will tell you that the best way to guarantee long-lived healthy fish is to buy top quality stock from local reputable breeders. This ensures you have fish that have not been overly stressed by transport, carefully bred for quality and grown on the best food.

If you aren't lucky enough to have a local koi breeder, or you've already bought your koi, not all is lost! In fact, most purchased koi are from national-level breeders, have been transported and do not have confirmed breeding standards. This doesn't mean you can't have great fish. It just means you need to be extra careful to quarantine and feed high quality food for continued growth.

Quarantining your koi fish is absolutely necessary for koi health. Every time you obtain a new fish (regardless of source), you need to quarantine your new koi for at least 4 weeks before adding it to your existing stock. If you don't properly quarantine, you risk introducing foreign bacteria and viruses into your stock. There are some fish illnesses, such as bacterial infections, flukes and worms that can kill your stock in one week after introduction.

Proper quarantine means no mixed water, food or contact between your existing stock and your new fish. When quarantining, you need to watch out for signs of stress in your new fish. Signs of stress and illness include a lack of appetite, discoloration on the scales/eyes, torn fins and lethargy. If you notice any such signs, there are several treatment options.

If your fish has torn fins or external lesions, you should treat with antibiotics administered with the fish food. If your fish isn't eating after several days, you may have internal parasites. Praziquantel (a.k.a. PraziPro) or metronidazole are very effective safe treatments for internal parasites, including gill flukes and worms. We recommend NOT using Potassium Permanganate unless you have exhausted all other options. Potassium Permanganate should never be used on fish with external lesions as it will burn their internal tissues.

After you've quarantined your new koi, and all goes well, you can add them to your pond! Depending on your bio-load and the number of fish you add, you may need to up your water changes. Already you should be changing at least 30% of your pond water a week to keep your pH stable and nitrates low. Adding more fish adds more waste to your filter, and it may take some time for new nitrifying bacteria to build up. Water changes keeps nitrites low if you've recently added a lot of new fish.

On top of water changes, you should regularly add salt to your pond. This isn't table salt or anything like that. We're talking about salt that's iodine-free and designed for aquarium and pond use. When you add salt to your pond, your koi will build up a thicker slime coat that supports a strong immune system. Pond salt also helps respiration in koi, and is effective in killing many common parasites. You should add 2 - 2.5 cups of pond salt per 100 gallons. You should only add more salt when you perform a water change (it does not evaporate).

For your koi, you should vary their diet instead of feeding the same pellet every day. This ensures they get enough nutrients from a variety of sources. If you have very young koi, it doesn't hurt to feed them a hearty supply of beefheart so they grow well. Also, it's okay and encouraged for your koi to eat some plants. This gives them plant fiber which helps prevent bloat.