In fall, it is common to see changes in your ponds water quality. Leaves from nearby trees and vegetation are falling in the pond causing the water to turn brown from the tannins in the leaves. The accumulated decaying plant life mixed with fish waste on the bottom of the pond is the perfect breeding ground for anaerobic bacteria as well as parasites that feast on the muck. Anaerobic bacteria will cause fowl odors, yellow or foamy water and ammonia or nitrites may be detected. Off colored water is not the only reason to remove the leaves from your pond, your Koi’s health depends on it. There are several signs that Koi will exhibit when water quality is bad or if there is a parasite problem. Here are signs to watch for that are not considered normal Koi behavior.
Laying Over, setting on the bottom acting lethargic
Fish seems to be lying on his side until you disturb him, then he swims a bit but goes back to lying over or if he stays at the bottom this is a sign of stress. It could be parasites but most likely, it is poor water quality. Test your water and perform a partial water change (be sure to add dechlorinator) and salt treatment.
Hanging or Gasping at the surface
Another sign of stress, as with a too low pH or not enough dissolved oxygen. If you see the fish hanging at the surface or if they have a milky film over them perform a major water change immediately, the pH is too low. The water change should bring the pH level to normal but you may need to add a stabilizer or pH puck to keep the pH level consistent. Gasping at the surface usually means there is not enough dissolved oxygen in the water. Poor water quality will also affect oxygen levels. Once again, a water change and salting would be in order, adding bubblers or a pump to help circulate the water.
Flashing, jumping and scratching
You know your fish; if they do not normally display this kind of behavior then you can assume there is a parasite issue. Perform a water change and contact your local Koi professional to learn about salt treatment and an over-the-counter parasite medicine should be added to the pond.
Swimming by itself, swimming head down or pop eye, bloated fish
These are signs of a bacterial infection. If you see a fish swimming alone staying away from the rest of your fish, not eating or swimming with his head down these are early warnings of an infection. Treat the water with an anti-bacterial medication and get antibiotic food to him. If you notice the eyes bulging or the entire body bloated, the scales seem to be sticking straight out then it is most likely too late for this fish. Remember an ounce of prevention is worth a pound of cure, in other words clean your pond, perform a water change or at the very least test the water before your fish starting acting up.