My betta fish isn't eating food from last week. He sinks at the bottom of the tank and color faded. What is the solution?enter image description here

  • please post the readings of your weekly water test AMMONIA-NITRITE-NITRATE-PH,how large is your tank what type of filter/pump do you have how long have you had this tank and have you cycled the tank properly before adding fish.you need to describe your problem more clearly(i am not able to read your mind) Commented Aug 16, 2019 at 19:01
  • 4-liter water tank. I cleared water 1 week. And already used Malachite Green and rock salt. Commented Aug 17, 2019 at 3:18
  • Bettas like 80 F water temperature , 90 F is fine. They can survive 70 F temperature but are lethargic. Start with checking the most obvious possibility. Commented Sep 9, 2019 at 15:33

3 Answers 3


You and your fish are a victim of the pet shop's lack of knowledge about fish and fish keeping.

Most likely your fish has ammonia poisoning as a result of not having cycled the tank properly. To cycle your tank properly please take a look here and do not add new fish to your tank until this is done.

The tank you have is too small for fish keeping, so you need to get a larger tank with proper filtration.

Using malachite green in your tank will kill all the good and bad bacteria, so never use any medication when you set up a fish tank. The only thing you need to add to the water is dechlorinator and nothing else.

Do not use rock salt in your fish tank, get aquarium salt from the pet shop and use this.

If you detect the presence of nitrite in your tank, you might add 0,3% of aquarium salt to protect your fish. You need to take regular water tests every week from your tank.

Sorry to say this, but the fish you have now will die soon; however, your next one will not if you cycle the tank properly.

  • 1
    Maybe it will not die soon. Or maybe it will. I was equally incompetent when I bought my first betta (my first fish ever), and the poor little guy went through all the experiments I made until I learned how to care for the aquarium. It eventually lived for several years.
    – virolino
    Commented Aug 23, 2019 at 11:11

Some basic advice:

  • learn how to cycle your aquarium at the beginning (this answer has a good reference about it);

Based on the advice about cycling:

  • add some gravel - it will accumulate dirt, and create an environment where the good bacteria will grow and do their job.
  • add plants;
  • be sure to have a mechanical filter;
  • after the first cleaning of the aquarium, NEVER wash it again; not chemically, at least;
  • never throw away ALL the dirt - it is full of good bacteria;
  • never fully disinfect the filtering medium in the filter; the good bacteria there is extremely important, and you need that colony there too;
  • never use chemicals for cleaning;
  • always use un-chlorinated water;

Ideally, do not use chemicals to de-chlorinate water. Put the water in a covered (but not sealed) vessel, and leave it for about 1 day. The chlorine will evaporate. I used to use bottled cheap non-gaseous water.


I agree with the others who mention cycling a tank and never cleaning the tank spotless. This will destroy the good bacteria. Beta fish have almost a set of lungs which are able to breath air and their body has adapted to thrive in murky water. If you go to a friend or local pet shop ask for some used filter media or substrate. You can place the used/dirty filter media in your filter or substrate at the bottom of your tank and it will help stimulate the beneficial bacteria growth. Unless you are positive and confident behind your use of MG to treat an identified infection, limit your usage to dips or a short term bath. This way you won’t contaminate the primary AQ with medication. Make sure you match temp, ph, hardness, ect or else the fish with be stressed.

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