Is my Cory sick?

[fxtrtr]

I had 3 Corys, one died. One is not swimming around much and the other was lethargic but has started swimming around more. My water temp is around 77°, the PH is 7.4, there is no nitrites or ammonia and nitrates is around 20 ppm. I do weekly partial water changes. The 10-gallon tank is several months old and fully cycled. I want to get other fish but if the Corys are sick, I don't want to introduce other fish to the tank. I give the sinking pellets of food and an algae wafer that I remove after one hour. Does this one look sick? I'm new to fish keeping so I cannot tell. I have not put any treatments in the water. I use a Penguin BioWheel filter.

 

[connorlindeman]

He does not look to be in the best of health...

 

[fxtrtr]

He does not look to be in the best of health...

Any idea why?

 

[Elena82x]

Any idea why?

How long have you had the tank and what else is living in it?

 

[Stefan3289]

Any idea why?

What % of the water do you change and how often? I also see you have gravel how do their bristles look? Also, have you measured the Gh of your water before?

 

[DoubleDutch]

The point is the food.
Corys aren't algaeeaters and those lack the needed minerals/vitamins/proteins

 

[Familyfishny]

I see a red patch near the gills, with maybe some blisters over it.

 

[GaryE]

All right, so I read your posting, so I won't ask for answers to questions you've answered. I see a young male who is thin. He needs careful feeding - not too much, of a high protein food. Try one of the bug bites types - they will appeal to Corys. Algae wafers won't. Corys eat small creatures in the sand in nature. They aren't scavengers or algae eaters.

With a small sinking pellet, each fish might eat 3 a day, max.

As the health of the Corys evolves, so will their social needs. You have a small tank that won't support a lot of fish, and I would suggest you only get Corydoras aeneus, as you already have. They are very social creatures, and 2 will not be happy or active. Adding 4 more will push the limits for space - it isn't ideal, but a few more would be a good minimum that tank would support if you do regular partial water changes.

Just grey Corys might seem boring, but they really are characters when they are in a group. I don't like keeping them in 10 gallon tanks, but you work with what you have. They can live very long lives for aquarium fish, so in the future, they will hopefully be there if you decide to or can upgrade.