Harlequin Rasbora- Fin Nipping?

Hi all,

I just got home from work and noticed that one of my albino Cory’s appears to have a nipped tail fin and is hiding under some drift wood.

I have a 29 gallon at 79 degrees. Just tested water and have 0 ammonia, 0 nitrite, and about 5-10 ppm of nitrate. My stocking includes 5 harlequin rasboras and 4 albino corys. I just got the 5 rasboras this past weekend with the intention of building the school up to atleast ten very shortly and probably add another albino Cory or two to the bunch.

Would the cory’s nip eachother? Or is it likely the harlequin rasboras potentially stressed from their current smaller schooling size?
Thanks in advance!

edit to add… I also think I might have some cory eggs on driftwood? so not sure if that might have something to do with it or not.

 

Well, I've never seen harlequin rasboras or cory cats nip fins. I guess anything is possible. But, if I was in your place, I'd also make sure to rule out some kind of disease or environmental hazard that may be causing the fin damage.

 

I have harlequin rasboras with peppered cories and have never seen them interact at all. The rasboras did nip each other at first to get the pecking order down but could care less about the cories. They don't even go after their eggs. Keep an eye on the tail- sometimes it can go from small missing piece to terrible quick. Any signs of fuzz need treatment immediately.

 

Well, I've never seen harlequin rasboras or cory cats nip fins. I guess anything is possible. But, if I was in your place, I'd also make sure to rule out some kind of disease or environmental hazard that may be causing the fin damage.

Thank you! I will definitely look into it more

I have harlequin rasboras with peppered cories and have never seen them interact at all. The rasboras did nip each other at first to get the pecking order down but could care less about the cories. They don't even go after their eggs. Keep an eye on the tail- sometimes it can go from small missing piece to terrible quick. Any signs of fuzz need treatment immediately.

Thank you! I will definitely keep an eye on it.

 

I've kept Harlequin Rasboras and Corycats for over a decade and have never seen either fin nip. I've kept them with very long-finned, slow moving fish that are often targeting by fin nippers without seeing the slightest damage.

I think it is much more likely that your Corycat has fin rot. That's a bacterial infection that can cause the fin to deteriorate. Despite being sold as "cleaner fish", Corycats are prone to bacterial infections of the fins and barbels if they are kept in a tank with a dirty substrate. It's actually especially important that they have a clean, smooth sand substrate for them to feed normally and stay healthy. You should thoroughly gravel vacuum the substrate each week, including under their hiding spots. And while they will need some sort of sinking food, if there's much leftover food you should lower the amount you are feeding.
If it is fin rot, you'll need to be careful about what medication to add to treat it. Corycats are scaleless fish and there are many medications that aren't safe for them. Dangerous medicines include anything with copper in it, such as Malachite Green or Victoria Green. You'll need to make sure that whatever medicine you get specifically says it is safe for scaleless fish and invertebrates.
My go-to medication for scaleless fish with bacterial infections is Tetracycline. It's safe for Corycats and can be used at a typical dosage, and is widely available at aquarium stores in the aquatic section.

Another possibility is that the fin was damaged somehow by sharp decor like lava rock or even by sharp/rough substrates like eco-complete or aragonite. You can check if your decor is sharp enough to damage fins by getting a length of pantyhose and running it along the decor. If the decor causes tears or runs in the pantyhose, it could also damage fins. Fins damaged this way can get a secondary infection of fin rot as well, in addition to the original damage.

Once you've found out what the root cause is and finished any medicine treatments that are necessary, your fish can regrow new fins. I've found that adding Stress Coat+ to the water will help them regrow their fins faster. Doing more frequent partial water changes to keep the water quality high is also important so the fin stays healthy as it is healing.

 

I've kept Harlequin Rasboras and Corycats for over a decade and have never seen either fin nip. I've kept them with very long-finned, slow moving fish that are often targeting by fin nippers without seeing the slightest damage.

I think it is much more likely that your Corycat has fin rot. That's a bacterial infection that can cause the fin to deteriorate. Despite being sold as "cleaner fish", Corycats are prone to bacterial infections of the fins and barbels if they are kept in a tank with a dirty substrate. It's actually especially important that they have a clean, smooth sand substrate for them to feed normally and stay healthy. You should thoroughly gravel vacuum the substrate each week, including under their hiding spots. And while they will need some sort of sinking food, if there's much leftover food you should lower the amount you are feeding.
If it is fin rot, you'll need to be careful about what medication to add to treat it. Corycats are scaleless fish and there are many medications that aren't safe for them. Dangerous medicines include anything with copper in it, such as Malachite Green or Victoria Green. You'll need to make sure that whatever medicine you get specifically says it is safe for scaleless fish and invertebrates.
My go-to medication for scaleless fish with bacterial infections is Tetracycline. It's safe for Corycats and can be used at a typical dosage, and is widely available at aquarium stores in the aquatic section.

Another possibility is that the fin was damaged somehow by sharp decor like lava rock or even by sharp/rough substrates like eco-complete or aragonite. You can check if your decor is sharp enough to damage fins by getting a length of pantyhose and running it along the decor. If the decor causes tears or runs in the pantyhose, it could also damage fins. Fins damaged this way can get a secondary infection of fin rot as well, in addition to the original damage.

Once you've found out what the root cause is and finished any medicine treatments that are necessary, your fish can regrow new fins. I've found that adding Stress Coat+ to the water will help them regrow their fins faster. Doing more frequent partial water changes to keep the water quality high is also important so the fin stays healthy as it is healing.

Thank you so much, that was incredibly informative! I did check my scape to see if I could find anything sharp and didn’t notice anything. I have sand, driftwood, and larger rounded stones with all live plants. Perhaps I need to check the driftwood more.

I haven’t had the Cory’s all too long, all of 2.5 weeks and too be honest it’s such a small tear/nip? that I am not sure If the Cory had it beforehand or not and maybe I didn’t see it. I only noticed now because he was acting more mellow than usual and saw the SLIGHT irregular shape upon a very close inspection.

Great info about the medications! I’ll be sure to keep an eye on it and diligently keep the water clean in hopes this might heal.