January 29, 2010

Jack Dempsey Cichlid Diseases, Prevention and Treatment

The primary reason aquarium fish get sick in the home aquarium is STRESS. Stress causes the immune system to weaken, leading to increased susceptibility to diseases and existing pathogens to flourish. A healthy immune system will go a long way in preventing disease and pathogen infestation. If you have problems, check for these stressful situations in your aquarium.

Recommended preventative treatments

Things that cause fish stress in the home aquarium:

  • Poor water quality: measurable ammonia or nitrites, or very high nitrates.
  • The water temperature is fluctuating more than 2 deg F/day
  • Incompatible species in the tank.
  • Overcrowding your fish tank (5 adult angelfish in 10g tank).
  • The tank is too small for the fish (foot long fish in 10g tank).
  • The water is too warm or too cold for the species (goldfish vs. tropicals).
  • Wrong pH for species (Discus vs. African cichlids)
  • pH fluctuations greater than 0.2 units/day.
  • Insufficient cover or hiding places present.
  • Wrong water hardness for the species (Discus vs. African cichlids).
  • Insufficient oxygen in the water.
  • Improper fish nutrition (wrong food, foods not varied).

Indications that your fish are stressed and in poor health:

  • Clamped fins (fins are held abnormally close to body)
  • The fish refuses its usual food for more than 2 days.
  • There are visible spots, lesions, or white patches on the fish.
  • The fish gasps at the surface of the water.
  • The fish floats, sinks, whirls, or swims sideways.
  • The fish shimmies (moves from side to side without going forward).
  • A normally active fish is still.
  • A normally still fish is very active.
  • The fish suddenly bloats up, and it’s not due to eggs or young.
  • The fish is scratching against tank decorations.

If your fish display any of these symptoms, you have a problem and should treat them immediately.

Aquarium medications to keep on hand:

I suggest setting up a fish medicine cabinet. It seems like fish always get sick when the store is closed.The following list of items should be kept on hand by all home aquariusts:

  • Water quality test kits: pH, ammonia, nitrite, nitrate
  • Aquarium salt (NOT table salt. Most table salts contain additives to keep them from clumping. Kosher or rock salt is OK).
  • Malachite green/formalin ich remedy
  • Methylene blue
  • Chlorine bleach for disinfection
  • Maybe one antibiotic (Kaynamycin or Furanace)
  • Antibiotic-containing food
  • Copper remedy for parasites
  • Q-tips
  • Malachite green or Mercurochrome


Common diseases/problems or What’s wrong with my fish?

Bad water quality
Fish are gasping at the surface, or very inactive, but there are not visible lesions when it first starts. Their fins may be clamped. Many fish of different species are affected, and possibly the whole tank. If the water has been bad for a while, the fish may have fin rot, or streaks of blood in their fins.

  • If fish are gasping at the surface, or have purple gills: high ammonia or low dissolved O2 may be the problem; test ammonia, dissolved O2
  • If the main symptom is inactivity: test nitrites, pH, dissolved 02, nitrates

Depending on your test results, try the following:

Change enough of the water to reduce ammonia levels to 1-2 ppm for freshwater or below 1 ppm for saltwater. If that means changing more than a third of the water, be sure the water you add is the same temperature, salinity, hardness and pH of the tank water. It is also okay to do multiple smaller water changes for a few days. Aerate, and make sure pH is at or below 7.0 for freshwater tanks. In addition to or instead of changing water, you can also add a dose of AmQuel to give fish immediate relief. Find out why ammonia is present and correct the problem.

Change enough of the water to bring nitrites down to below 2 ppm (as with ammonia, if this is a lot of water, match water parameters or do multiple water changes), add 1 tbsp/gallon salt (not all fish may tolerate this much — start out with 1 tsp), and add supplemental aeration. Find out why the nitrite levels are high and correct the problem.

Change water and clean the filter. If your filter is dirty, there is more waste material present to break down into nitrate. Start feeding less and changing water more often.

Low oxygen
Run an airstone. If this helps a lot, the fish probably don’t have enough oxygen in the water. Your tank may need cleaning, fewer fish, or additional water movement at the surface from a powerhead, airstone, or filter.

Improper pH
If pH is too low: make sure carbonate buffering is adequate — at least 5 dKH. In general, adding baking soda at 1 tsp. per 30 gal. raises dKH about 2 degrees. For a 10-20g tank that just needs the pH a little higher, try about a quarter teaspoonful. If that isn’t enough, add up to a teaspoonful more. You can scale this up to 1 tsp/30 gal for larger tanks. If the pH is still too low and the KH is at least 5-6 dKH, clean the tank. For long-term buffering in saltwater and alkaline freshwater systems, add crushed coral. If pH is too high, pH down (phosphoric acid) can be added. Don’t rely on this stuff, except in extreme situations like ammonia poisoning because it can cause excessive algal growth. To lower pH long-term, filter over peat, or use distilled or deionized water mixed with your tapwater.

Freshwater Ich
Symptoms: Fish look like they have little white salt grains on them and may scratch against objects in the tank.

White spot disease (Ichthyopthirius multifiliis) is caused by a protozoan with a life cycle that includes a free-living stage. Ich grows on a fish –> it falls off and attaches to gravel or tank glass –> it reproduces to MANY parasites –> these swarmers then attach to other fish. If the swarmers do not find a fish host, they die in about 3 days (depending on the water temperature).

Therefore, to treat it, medicine must be added to the display tank to kill free-living parasites. If fish are removed to quarantine, parasites living in the tank will escape the treatment — unless ALL fish are removed for about a week in freshwater or three weeks in saltwater systems. In a reef tank, where invertebrates are sensitive to ich medications, removing the fish is the only option. Some people think that ich is probably dormant in most tanks. It is most often triggered by temperature fluctuations.

Remedy:For most fish, use a medication with formalin and malachite green. These are the active ingredients in many ich medications at fish shops. Some products are Kordon’s Rid Ich and Aquarium Products’ Quick Cure. Just read the label and you may find others. Check for temperature fluctuations in the tank and fix them to avoid recurrences. Note that tetras can be a little sensitive to malachite green, so use it at half the dose.

Use these products as directed (usually a daily dose) until all of the fish are spot-free. Then dose every three days for a total of four more doses. This will kill any free-swimming parasites as they hatch out of cysts.

Another remedy is to raise the tank temperature to about 90 deg F and add 1 tsp/gallon salt to the water. Not all fish tolerate this.

Finally, one can treat ich with a “transfer method.” Fish are moved daily into a different tank with clean, conditioned, warmed water. Parasites that came off of the fish are left behind in the tank. After moving the fish daily for a week, the fish (presumably cured) can be put back into the main tank. The disadvantage of this method is that it stresses both fish and fishkeeper.

Fin rot
Symptoms: Fishes’ fins turn whitish and die back. Fin rot often follows damage or injury. It can also be caused by poor water quality.

Remedy:First, fix the water and remove any fin-nipping fish. Change some water (25% is good) and add 1 tsp/gallon salt to promote healing. If bad water quality or an aggressive tank mate was the problem, that should be adequate. Healing will begin within a couple of days.

If it worsens, decide first whether it’s fungal or bacterial. Fungal fin rot looks like clumps of cotton on the fins and usually follows injury. It is commonly seen in African cichlids or fish that have injured themselves against decorations. Bacterial fin rot is whitish, but not cottony (unless it’s columnaris), and can be contagious. The fish then need to be removed from the tank and medicated.

Fungus: For fish large enough to handle, catch the fish, and dab malachite green directly on the fungus with a Q-tip. This is extremely effective. Repeat treatments may be necessary.

For small fish, a commercial fungicide such as Maroxy may work. For severe infestations, try a bath in methylene blue (enough so you can barely see the fish) until the fungus turns blue or for 20 min. If you add methylene blue directly to a tank, you will kill plants and trash your biological filter.

Bacterial: Antibiotic treatment in a quarantine tank. This is stressful for the fish, and doesn’t always work, so be sure of what you are doing before you attempt it. If the fish is still eating, the best bet is an antibiotic food. Tetra makes one that works well — just buy the one for bacterial diseases and follow the directions on the can.

If the fish is not eating, a bath treatment is necessary. A combination of Kaynamycin and Furanace usually works, especially for Columnaris. Again, treat in a separate tank and aerate heavily.

Cichlids and other “scrappy” fish may sustain injuries that are severe enough to draw blood from fighting. Other fish may run into tank decorations, walls, or rocks.

Larger fish can be netted and their injuries dabbed with Mercurochrome (available at drug stores) or Betadine (iodine-based antibiotic also available at drug stores) to help prevent infection. Be sure to keep these chemicals off of the gills and eyes. For really small fish, put the affected fish in dilute methylene blue (pale blue) and 1 tsp/gallon salt in a separate tank. If you want to keep the fish in the main tank just add salt, as methylene blue will trash your biological filter.

Watch the fish to be sure injuries are healing cleanly, and repeat the Mercurochrome dosage if necessary. If fin rot or fungus sets in, see the above section on fin rot.

Fish swells up like a balloon and may show popeyes. It may recover with no treatment and may die despite it. The swelling is because the fish is absorbing water faster than it can eliminate it, and it can be caused by many different problems. High nitrates are one thing to check. Internal bacterial infections, including fish TB, are other possibilities. If there are no water quality problems, you may want to attempt antibiotic treatment in a separate tank.

Head and Lateral Line Erosion (hole-in-head disease)
This disease can affect discus, other cichlids, and many saltwater fish. The fish develops holes in it’s head and sometimes along its lateral line. Causes are unclear but as in any disease, stress and poor water quality likely play a role. Fish in planted tanks rarely get HLLE, which supports the nutrition idea, since fish can nibble on the plants and obtain extra nutrition. With large cichlids such as Jack Dempseys that rip up plants, feed Spirulina, lettuce or Kale often. Untergasser also observes that the protozoan Hexamita can be found in the lesions. Untreated cases can eventually prove disfiguring or fatal.

Remedy: First, make sure water quality is optimal and reduce stress. Stopping carbon filtration may help as it can remove nutrients from the water. Then feed a vitamin-enriched food, paying particular attention to vitamin C supplementation.

For stubborn cases, some books suggest metronidazole (Flagyl) to eliminate Hexamita (a mildly pathogenic protozoan) from the lesions. Your mileage may vary with that one. Metrozole and Hex-a-mit are commercial medications with metronidazole.

Swim bladder disorders
Fish floats upside-down or sideways. This is particularly common in fancy goldfish because of their bizarre body shapes. Dry food eaten quickly swells up in the fish’s intestine and keeps the fish from controlling its swim bladder properly.

To help, feed the fish pre-soaked or gel-based foods. Green foods are also helpful; peas in particular.

As with fin rot, these disorders can also be caused by bacterial infection. Treatment is much the same. Use antibiotic food if the fish is eating, or add antibiotic to the water in a quarantine tank if the fish is too sick to eat.

Large external parasites (as opposed to ich)
Add a copper remedy to the tank and monitor it with a copper test kit. Also, Mardel’s Maroxy works well. For anchor worms or leeches on pond fish, remove them from the affected fish with tweezers and swab the area with Mercurochrome to prevent infection.

Fish look like they have been finely dusted with flecks of gold. Fins may be clamped and the fish may shimmy.

Treat with an anti-parasitic medication such as copper or formalin/malachite green.

Keeping your tank free of disease

Quarantining new fish is a good habit for all aquaria, but is not absolutely necessary for success. Quarantining is simply keeping a fish in a separate tank for long enough to be certain that it is disease free. Many beginners do fine without a quarantine tank, and object to the cost of another setup. A quarantine tank does cost more, but if a hobbyist has hundreds of dollars invested in fish, it is cheaper to have a separate quarantine tank than to replace fish killed by a newly introduced disease. Also, many of us become attached to fish and do not want to expose our pets to diseases from newcomers, no matter what the cost.

The purpose of quarantining is to avoid introducing new diseases to a stable system, and to be able to better observe new fish for signs of disease. A quarantine tank can also double as a hospital tank for sick fish. Hospital tanks are good because they lower the cost of using medicines and keep diseased fish separate from healthy ones. Quarantine is probably most important for saltwater tanks/reef systems because of the difficulty of treating diseases, or wild-caught freshwater fish because they are probably not disease-free. Quarantining itself can stress fish so be sure quarantine is as stress-free as possible.

How to set up a quarantine or hospital tank:

  • Keep an extra filter — a sponge filter is ideal — or piece of filter floss in an established tank, so that you don’t have to keep the quarantine tank set up at all times. Some people choose instead to keep the filter going with guppies or danios (for freshwater) or mollies (for saltwater).
  • If you don’t keep the tank running, use old tank water to fill the tank. So: old tank water + established filter = instant established tank.
  • Add a spare airpump and heater. If you haven’t messed with the heater during storage, it should come to wherever you had it last time.
  • Consider using Amquel or equivalent when medicating the tank in case the biological filter bacteria are sensitive to the medication. Sick fish are especially susceptible to ammonia. (Note that ammonia which has been bound with Amquel still shows up on a nessler ammonia test. So, if you are planning on testing for ammonia in that tank, you need to use a salicylate ammonia test.)
  • For a hospital tank, do small, frequent water changes (even every day).

If possible, quarantine all of your new fish for about three weeks. During that time, gradually acclimate the fish to your tank’s parameters: hardness, pH, salinity, temperature, etc., and watch for and treat any signs of disease. Do not medicate quarantined fish “just in case.” Only treat evident, definitely identified diseases. Treating all quarantined fish with a bunch of medicines will just lead to weakened fish and antibiotic resistant bacteria.

Once you are done with the quarantine, if you treated any especially nasty diseases, it is good to disinfect the tank and reestablish the filter. Chlorine bleach or strong saltwater (for freshwater) work well. Be sure all traces of bleach are rinsed off. Another good disinfectant is potassium permanganate (Jungle’s Clear Water is one commercial way to get it).

If you choose not to quarantine, do not add store water to your tank with the new fish.

Q: How about quarantining plants?

A: Plants can carry diseases into a tank, too. It is a good idea to disinfect new plants if there were fish in the tank with them at the store.

Q: How do I avoid introducing diseases in the first place?

         A: Never buy sick fish from a store. Especially do not buy fish or plants from a tank if *any* fish in the tank shows any signs of disease or if there is medicine in the water (water is colored yellow, green, or blue). Store people may say the fish are fine, but if they were, why is the medicine in the tank? Also ask how long the fish have been in the store. New arrivals may be carrying diseases that have not shown up yet. It is better to wait a couple of weeks before purchasing the fish. If you must have a fish that just came in, be especially sure to quarantine it properly. 


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  • Holly Drago

    March 15, 2010 at 11:06 pm

    to “paint” the fish, where to purchase Mercurochrome? i can no longer find the stuff…

  • jimmy

    September 25, 2010 at 8:55 pm

    I have a large jack dempsey that mouth is stuck wide open, it has been that way for 4 weeks now. I can not find any info or anyone who has ever heard of this, please help he is losing weight. any info would be appreciated.

    • Tina

      February 1, 2011 at 10:49 pm

      I had that issue with an Oscar. I did more frequent water changes, added a bit of salt and it went away. I did read someplace that happens when fish is exposed to poor water quality for long lengths. Not sure if that is true, but now I do weekly 25% water changes and once a month I do 50% never had that problem again

  • Dave

    February 17, 2011 at 6:11 am

    Whats the growth rate?

  • wayne

    April 12, 2011 at 11:37 pm

    I have a jack dempsey that dosnt seem to grow how can i help along

    • Your Name

      February 17, 2012 at 8:34 pm


      You posted this a while back. I hope you got your Dempsey to grow. I bought my Dempsey at 2.25 inches 1 year ago…he’s now full grown. I fed him a standard diet of cichlid sticks and then earthworms and bloodworms at least 2-3 times a week. He grew fast.

  • Ryan

    May 24, 2011 at 4:04 pm

    I have a female Dempsey who lay’s on her side at the bottom of the tank. Has anybody experienced this before and what did you do to fix it?

  • Annette

    August 23, 2011 at 1:54 pm

    My jd is at the surface not gasping. I’ve had one die already a couple of weeks ago and I’m worried about the second one who just started surfacing. The water quality is good. They are over 8 years old. Could they be dying of old age? Visibly they look great just not acting right. Please help.

  • mechelle

    August 30, 2011 at 11:59 pm

    Is there anything that can be done for my Jack Dempsey?? Laying sideways face down, with a big bulge on it’s left side (upper). It’s been this way for a week :(

    • Diahann

      December 7, 2011 at 4:01 am

      Did you get any information on this issue? Mine has been like this for about 4 weeks, looks almost bent. There are times when he staightens out and does some laps in the tank but then goes right back the bottom in this posture.

      • Rachel

        January 3, 2012 at 6:54 am

        I have a jack that is doing the same its been a few weeks also.?

        • Kevin

          July 21, 2012 at 3:45 am

          So my young female jack Dempsey was doing the same thing, laying on side near the surface. I read several places this is most likely swim bladder disease. It can come from over feeding, or not mixing up their diet. Basically sounds like constipation. I also read that you should of course feed them different things, including veggies. For a few days I have been feeding them blood worms, brine shrimp and vegi blend, And she seems to be doing a lot better.

  • thomas

    September 13, 2011 at 1:40 pm

    iu have a jack dempsy that is not being actie not eating much and hiding all day and night

    • jackarthur46

      September 13, 2011 at 7:38 pm

      Inactivity is very common for Jack Dempsys, especially if they are young and small. If there are other, larger and aggressive fish in the aquarium, they will keep the JD in seclusion until they grow larger. If it gets hungry enough, it will eat. Good luck

      Jack . . . The World Of Jack Dempseycichlids

  • Your Name

    October 21, 2011 at 8:50 am

    i have a jd and his eye are glaze over whitee and idk whats going cant figer it

  • Kim

    November 22, 2011 at 4:39 pm

    I have a jack demp fish he dose not want to swim the fins are close to his body what can i do to help he and do i need to take he out of the tank with my other fish so that it want make them sick

  • Jack Elwood

    December 19, 2011 at 1:15 am

    I havea Jaguar CICHLID, a PEACH TYPE CICHLID, ELECTRIC YELLOW AND A JD WITH A PLECO. All my water is checking out cool, I keep a floating thermo at 80 degrees, i put chemicals in for ph, other chemicals for water clarity. My pleco had a cut on it’s side and I administered MELAFIN for a week then a water change. During that time I watched the cut heal. IS THERE ANYTHING I AM FORGETTING AT ALL BECAUSE I AM STILL A NOVICE.

  • boombox

    March 3, 2012 at 7:01 pm

    my jd has white stuff on his eye’s and i dont know what it is i need help does anybody know

  • arel

    March 28, 2012 at 11:00 pm

    hi I noticed my JD had a red dot on his forehead yesterday now it looks like a pinkish red pimple he is full grown is this normal any help would be appreciated ty

  • Kim

    April 11, 2013 at 4:55 pm

    I know someone who has a JD fish. He has one that he has had for years then he recently purchased another one. The new one was doing fine for a couple of weeks. Then it startered swimming funny, it kinda looked as if it was floating around and sorta drifting with the current of the tank. I told him to try the pea thing well today is the third day it wont eat the peas and now it lays on the bottom of the tank on its side and doesnt really move and its eyes look bugged out. its not dead it is still breathing. Is there a way to save it or is it to far gone?

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