I came home after work today to my baby guppy tank showing signs of sickness.

About 50% of them are gasping for air. I just did a 50% water change, after using my master kit, and seeing that my ammonia and nitrites were a little higher than usual, not toxic levels, but higher than I like to keep it. I have one corydora, and he seems to be fine, but I'm not seeing OTHER signs of sickness. I do weekly 10-15% water changes, and about a week ago completely changed the gravel. My airater, filter and heater all seem to be working fine (78°F) and I do not see film, building eyes, spots or lacerations. I'm curious if dosing with an anti-parasitic AND a fungus medication will do further harm, being that I can't figure out the EXACT issue??

It's strange that my ammonia would be higher than normal because I feed the same amount daily, and I never change my filter cartridges (just rinse everyone in a while) to keep healthy beneficial bacteria. My mind is blown and I don't want to lose my babies, but don't know what else I can do. I'm also at odds as to quarantine the ones that are at the top and JUST treat them, or to treat the entire tank, if treating them IS the general recommendation.

  • 1
    What are the exact levels of ammonia, nitrite and nitrate? In my experience, even trace amounts of ammonia can be lethal to fish.
    – Henders
    Oct 17, 2017 at 8:11

1 Answer 1


By changing the gravel you have removed an overly large portion of the bacteria.

Stop feeding and angle the water outlet from your pump/filter upwards to get more movement of water in the surface (to get more oxygen in the water).

Use some water from one of your other tanks when you change water if this is possible to do.

Medicating the whole tank will kill the bacteria, so it is best to avoid this.

Add some aquarium salt to reduce the effects of ammonia and nitrite on your fish.

Test the water daily and start feeding the fish slowly when the water is normal. At first, start by feeding only once a week and if the water stays good, you can slowly increase the frequency of feeding.

A little about the two types of bacteria in the nitrogen cycle:

These two types of bacteria form a layer, first Nitrosomonas (they use CO2) and on top of them the Nitrobacter grows (they use oxygen - O2).

Additional information can be found in the two links provided.

  • Dang, @trondhansen I didn't realize changing my gravel would throw everything out of wack. Do you think I should add some Cycle to my tank when I add the aquarium salt, to increase beneficial bacteria? Since when I did the water change a few hours ago I used fresh? The change seemed to help a little temporarily
    – Christy B.
    Oct 17, 2017 at 6:54
  • the most important thing is to stop the feeding until the bacteria can multipy and cope with the waste in your tank it will probably only take a short time as the bacteria in your filter is still alive and will help seed the gravel in a short time.even if you add bacteria they still needs some time to multiply. Oct 17, 2017 at 10:21

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