Recent Questions
     Pond Fish

Q. Hi, I have a 12 inch Koi, about 8 years old that has an ulcer on top of it's head for many years already. The ulcer is oval, about 3/4 of an inch in length and 1/4 of an inch deep. What can I do about it? Thanks Ahead! Aris

A. Hello Aris, Koi ulcers are holes that develop on the exterior of a fish--usually on the flanks or underbelly--caused by infection by the aeromonas bacteria, which in turn follows infestation by a parasite. Ulcers can also be caused by abrasions and scratches that have penetrated the fish's protective slime coat. They are found more frequently in the spring, when the koi's immune system is at its weakest, and in fish that have been resting on a pond bottom that is excessively rough, causing a "bed-sore" type of ulcer. Koi ulcers usually begin as a single raised, reddish scale, and then develop into open wounds that become progressively deeper and larger.

Ulcers on your koi are usually an indication of poor water quality, which must be corrected in order for the fish to be able to heal.
Keep your pond well-planted with both marginal and surface plants, which aid water quality by absorbing dangerous ammonia and nitrites, as well as adding oxygen.Use a biofilter containing beneficial aerobic bacteria to further purify waste products in the water. Replace the filter as needed and to maintain the health of the aerobic bacteria, keep the filter running around the clock. To reduce the amount of waste left from feeding your Koi, use a high-quality commercial fish food and offer small, frequent feedings.
To cure your koi of ulcers, you must not only correct poor water quality, but treat for parasites and bacteria. Use a pond salt bath, in a separate holding tank as a natural antibacterial agent. There is an article of this procedure coming up in this April’s newsletter, entitled “Fishy Day Spa”. A more aggressive treatment, recommended by Koi Ulcer website, is to give a one-time-only treatment to your koi's ulcer by gently netting the fish and cleaning the ulcer with hydrogen peroxide on a cotton swab.

Please keep us informed, and send pictures if you can.

Q. Hi, I have some older goldfish in a aquarium, during the warmer months they are in my pond, 2 of them seem to have gotten a deep red edge around their bodies almost looks like blood and they slowed down, is this a health problem, everything seems ok with the aquarium, thank you for your time!

A. Hello John, Streaks are often caused by poor water quality. Use an aquarium or pond water test kit to check your water parameters. As a minimum you need to test for ammonia, nitrite, nitrate, and pH. Some koi vets associate red streaks with either high nitrate or with low oxygen. In either case a partial water change should help. 
On some fish (goldfish in particular) that are very light in colour, you can see bloodlines on their tails. This seems to be just a natural thing so if keeping nitrates low and having plenty of aeration do not help, and the fish is acting healthy otherwise, consider these streaks normal. If attending to your water is not helping and the fish is still looking lethargic, it is likely a bacterial infection has set in. Treat by feeding antibiotic food or if the fish is not eating, use a full spectrum water antibiotic like penicillin and tetracycline. You’ll need to consult a vet to obtain a prescription for any meds. Adding salt to a separate holding tank, and giving the fish a “spa treatment” can also help. See the next article in the April 2011 Newsletter – ‘Fishy Day Spa’

Q. I have a large three year old koi that has been wintered for two winters. This spring I noticed that it seems to stay in a shallow area and is not feeding or moving around very much until disturbed and then seeks another shallow area in which to rest his body where there is some support. Should I isolate this fish and what could the problem be?

A. Hello, So sorry to hear your pond pet isn’t feeling well.  If your Koi does appear ill (sluggish, swimming alone, hugging the bottom of the pond) place it in a separate tank until treated, so it can’t potentially harm others in the pond.
All fish ailments are diagnosed using the same procedure: First you examine the history (i.e. recent handling, water temperature , crowding, untreated water, etc.) then you examine the fish for patches, clamped fins, red scales, white spots and any other signs of infection. Finally, and without exception, you must test the water.
Until you have performed a diagnostic, you won’t be certain which fish medication or treatment to use. These symptoms can be caused by bacterial infections, parasites, fungus, etc.  Our recommended site for Fish Health and diagnosis is www.koivet.com . If you need any help, feel free to send in pictures of the ‘patient’ or bring in a water sample to the retail store.

Q. I have a koi pond, i heard you can add crayfish to help keep it clean. that doesn't sound correct because crayfish eat fish. my koi are good size, if it is true what breed of crayfish would you recommend?.

Thank you, David

A. We don't recommend you add crayfish, clams, snails or any other "non-fish" creature to your pond as they can very easily upset the natural balance of your water chemistry and possibly foul up the filtration system. Also, it's best not to include any predatory fish into your ecosystem, like bass or pike unless you have an enormous pond (ie: >250,000 gallons). Stick with koi & goldfish. They are more colourful anyway.

Q. My fish are gathering under the waterfall, some are even trying to
jump it, what gives?

Thank you ,
Denise Vierich .

A. Have you ever been in love? If so, did you feel like jumping and swimming naked under a waterfall? No worries. It's all part of the dating routine for fish.

Q. Our pond has goldfish in it. Nothing fancy. In the past we had water hyacinth and water lettuce floating around plus oxygenators. The problem is the fish eat the floaters. Any suggestions?

Many thanks,
Alma.

A. If you feed your fish, they will eat less of the plant material in the pond. Also, if you add more lettuce and hyacinth, they won't be able to consume the plants as fast as they grow. Imagine if you had to eat nothing but lettuce every day then suddenly someone offered to cook you a beautiful four course meal. You'd probably eat less lettuce.

Q. Dear Dr. Pond,

How deep does my pond need to be in order to keep fish over the winter?

A. Most people think that their pond needs to be built below the frost line in order to keep fish over the winter. This is a very common myth, especially in colder climates when in fact there are thousands of thriving two-foot deep ponds all over the country. The water in your pond will only freeze eight inches down, even in Canada, because of the insulating qualities of the earth that surrounds the pond. If you build your pond deeper than two-feet, you now have a "swimming pool" by most municipal standards and you now must erect a safety fence and contend with strict building codes and permits. A deeper pond only means more work with no real added benefit.

Q. Dear Pond Doctor,

I think a raccoon is eating my fish. Every few days, 2 or 3 more are missing. What can I do to prevent this?

A. When you go out to enjoy your pond in the morning and you notice that a few fish have gone missing, it's very tempting to blame raccoons, cats, and other critters.  Before you go setting up traps, consider the following facts.  Most four-legged creatures, including raccoons, generally prefer to stay dry.  Sure, they may hang out on the side of your pond and try to take a swipe at your favorite Koi or Shubunkin but fortunately, most fish will swim to deeper water out of harms way when threatened.

One predator you do need to watch out for is the blue heron because they don't mind wading in for the occasional Koi canapé. The best solution is to set up a decoy or a Scarecrow motion-activated sprinkler along side your pond.  A surprise jet of water does well in warding of these waders and doesn't harm the bird other than bruise their avian ego.  It's a good idea to move the decoy or sprinkler around once in awhile to keep them guessing.

Giving your fish places to hide also helps increase their odds of survival.  Rocks and short sections of PVC pipe can be used to build miniature caves in the walls and ledges of your pond.  Aquatic plants like lily pads work well too, by creating a natural camouflage that has the added benefit of keeping your Koi cool on hot summer days.

Q. Hello there, 

This is the 3rd spring with my pond and, for the
first time, it appears that a couple of my fish may have some type of parasite (I'm not really sure)???  The one koi looks like it has a small white "tick" attached to his face area.  Fortunately, it is almost gone now. I believe that the warmer water has allowed the koi to defeat whatever this thing was all on his own.  His appetite has been super all spring and he has no clamping of fins or anything like that.  My water quality has been excellent all winter and this spring, so I'm assuming that he picked it up from all the frogs, toads, and birds???  Anyway, my question is do you think I should treat this  fish for parasites or just let him be since he appears
to be healing all on his own?  Many Thanks,  Britt

A. It sounds like the fish had a mild case of  Ichthyophthirius multifilis, otherwise known as Ich or White Spot disease. It might also be Lernaea, otherwise known as Anchor Worm. Click Here for information on both disease conditions.

I hope this helps.
Amor vestry aqua hortus,
Nicholas L. Bott, CIT, CAC