Corys not eating

[Jesse2016]

Hi,

I have a 20 gallon freshwater tank with two albino corys, one angelfish, two red eyed tetras and a black skirt tetra. The corys have been reacting very strangely in the tank and are constantly swimming up and down the sides of the tank. It looks like they are eating algae but the problem is they are not eating when we feed the fish. (When the flakes fall to the ground corys usually clean it up). The corys are beginning to look really gaunt and thin so I'm worried this might be a water issue. (I'm not very sure on the nitrate or nitrite or ammonia levels as I don't have a kit). But if anyone can tell me why the corys are behaving this way that would be much appreciated.

 

[nic1]

You should get a kit. The corys are bottom dwellers and any spikes usually start from there where all the fish waste and uneaten food fall.
20 gallons is too small for an angel, I think your problem is your stocking. Tetras need space to move and swim fast like they do.
A combination of water parameters and stress throughout the tank is the likely cause.

 

[nic1]

I hit the post before I finished!
Tetras like to be in groups they are a shoaling fish, if they are in very low numbers and are kept singly, they become nippy and will pick on anything. I think they are picking on the corys also.

 

[Jesse2016]

Yeah the angel is definitely too big for the tank and has outgrown the tank. Originally we had a 40 gallon tank but it sprang a leak so we had to switch to the 20 gallon. But once we switched there were some problems with the new water and cycling of the new tank, and most of our fish died. But this was about 2 years ago, so I'm not sure why the cycle hasn't been established in my 20 gallon tank yet. I've also noticed the filter material is really clean all the time so I'm thinking there's not enough aerobic bacteria to form the cycle in the filter media. I'll look into buying a kit if it's not too expensive. I"ll also do some water changes as soon as possible tomorrow. Thanks for the help!

 

[FroFro]

Yeah the angel is definitely too big for the tank and has outgrown the tank. Originally we had a 40 gallon tank but it sprang a leak so we had to switch to the 20 gallon. But once we switched there were some problems with the new water and cycling of the new tank, and most of our fish died. But this was about 2 years ago, so I'm not sure why the cycle hasn't been established in my 20 gallon tank yet. I've also noticed the filter material is really clean all the time so I'm thinking there's not enough aerobic bacteria to form the cycle in the filter media. I'll look into buying a kit if it's not too expensive. I"ll also do some water changes as soon as possible tomorrow. Thanks for the help!

Do you have any sinking shrimp pellets? My cory's swim all over the bottom and walls of the tank just looking for food and when I drop them in they gobble them up. My cory's never seem much interested in any flakes that fall to the bottom when I feed my angels, perhaps that's why they don't seem to be eating? But you should also follow the above posters advice to, get a test kit and check your water parameters. You could also go to your local LFS and ask them to test your water, make sure you tell them specific numbers. Big pet stores usually use test strips and while these are not 100 percent accurate they are better than nothing. Best of luck!

 

[NickAu]

(When the flakes fall to the ground corys usually clean it up).

Flakes are not the best option, What type are they? Pellets are a better option. What else are you feeding them?

 

[Byron]

Yeah the angel is definitely too big for the tank and has outgrown the tank. Originally we had a 40 gallon tank but it sprang a leak so we had to switch to the 20 gallon. But once we switched there were some problems with the new water and cycling of the new tank, and most of our fish died. But this was about 2 years ago, so I'm not sure why the cycle hasn't been established in my 20 gallon tank yet. I've also noticed the filter material is really clean all the time so I'm thinking there's not enough aerobic bacteria to form the cycle in the filter media. I'll look into buying a kit if it's not too expensive. I"ll also do some water changes as soon as possible tomorrow. Thanks for the help!

The 20g has certainly "cycled" after 2 years with fish, so this is not the problem. As for the filter media being "clean," you can't see bacteria; they colonize surfaces like the filter media, substrate, and many other places. The brown gunk that often appears in filters is organics.

To the corys behaviour...this is generally the result of stress. It is common when corys are first introduced to an aquarium (they do not like being moved), and some species are naturally more active (panda corys will regularly swim into filter currents, etc). But from your other information, I would suspect they are highly stressed. They must have a smal,l group, at least five, but more is always better (when space permits), as they are highly social fish and without a group they will feel threatened. I understand the tank issues explained, but you must do something or you are going to lose fish, or at the very least they will not be healthy.

First is to remove the angelfish. This fish should attain a decent size and almost fill the entire volume of a 20g. And other fish like tetras, especially those species mentioned, are notorious for fin nipping which stresses the angelfish even further. And the lack of groups for each tetra species only adds to their stress. A 20g is not large enough for decent sized groups of both tetras, and here black skirt tetras are not going to work long term, so I would re-home this fish too. Then you can increase the corys to five (if you want to keep them), and the red eye tetra to at least six, if you want this species. It is not really the best in a 20g, being fairly active.

As mentioned by others, corys need sinking foods like shrimp pellets, disks, tabs. They will not eat "left-overs" and cannot be healthy on them even if they do out of desperation.

Byron.

 

[Jesse2016]

Flakes are not the best option, What type are they? Pellets are a better option. What else are you feeding them?

The flakes are Tetramin. We used to feed algae disks but it created a lot of algae growing in the tank. I will consider buying shrimp pellets for the corys. I didn't know they don't like "left overs" I always thought they were the cleaners in the tank scavenging off scraps.

I will look into rehoming the angelfish, perhaps to a specialty fish store nearby and hopefully they will take her in.
Thanks so much for the help, I really do appreciate it.

As an update, after the water change today the corys seemed to like digging in the ground a bit more but they still are swimming up and down the sides of the aquarium.

 

[Essjay]

The algae discs were not the best diet for cories as they are not vegetarian fish. They are omnivores and need animal protein in their diet, which is why the others are recommending shrimp pellets - that's pellets containing shrimp not pellets for feeding to shrimps.

 

[NickAu]

As an update, after the water change today the corys seemed to like digging in the ground a bit more but they still are swimming up and down the sides of the aquarium.

Are they going all the way to the top for gulps of air?

 

[Jesse2016]

Are they going all the way to the top for gulps of air?

No they aren't going all the way up to the top for air but are just swimming up and down the sides.