Tropical Fish Site

Profiles Reviews Guides for Tropical and Marine

My Tropical Fish Seems To Be Breathing A Lot

As a general rule your tropical fish’ mouths should remain closed except for a few circumstances which are that they are eating, yawning/stretching or recovering after a fight or being chased. Apart from the chasing which does happen depending on the type of fish you keep the others are normal.


If however you find your fish is constantly opening and closing its mouth then you need to address the problem as their mouths should stay closed. The primary cause of a tropical fish appearing to breath a lot is down to there not being enough oxygen in the water, they therefore have to use their mouths to suck in oxygen rather than take it in through their gills. This is far from ideal and although preventative methods can be put in place to overcome this, such as adding powerheads or air stones to create bubbles. Both methods will increase surface water movement which will increase the oxygen in the water however in the interests of there being a power cut this is not necessarily a safe option. We have put together a brief guide on what you could do with your fish tank during a power cut so we won’t touch on that here.

It is especially an issue if your fish are breathing a lot at the top of the surface, again, we have discussed what the cause of this may be in our guide to what to do if all your fish are at the surface of the water. This is an extreme case of lack of oxygen in the water though but the principal is the same. Ultimately your fish tank is overstocked too much if the fish are constantly breathing a lot in the water.


So the best method and way round this is to reduce the number of fish in your aquarium by re-homing to another tank or another enthusiast. Most local fish stores are good enough to take fish back too if you have no other option. We would advise that you check how heavily stocked your tank is initially before purchasing more fish, take a look at our guide on fish tank stocking levels if you are not sure what this is.

You should also check if you have enough surface water  movement and if not you should invest in a powerhead to promote this surface water movement.

There is a chance this could be down to swim bladder disease so check out the other symptoms too so you can rule this out.

Most local fish stores are very knowledgeable and if you are unsure then ask before purchasing the fish as it can become costly taking the fish back as you’re unlikely to get your money back! If you are positive and 100% sure that the stocking levels are fine and the tank is well understocked and there is only one fish breathing heavily then observe the fish closer to see if there are any other symptoms such as skin abnormalities or other out of character behaviour and investigate these further.