Corydoras and antibiotics?

Hi everyone, I’m pretty new to the hobby and am having some problems with my corys. I have 6 bronze, 5 peppered and 2 leopard corys in a 180 litre (47 gallon) about a month ago I added 4 more leopards. The first one died in a couple of days and then one a week after that. They would become lethargic and just sit in one spot with their dorsal fin clamped down, heavy breathing, becoming pale and just before they died they would get a red spot near their gills and belly. The last one seemed to have a white fuzz on the red spot, I treated him for fungus but he died soon after. They also had very small barbels. Now the original two leopards and one of my younger bronze are acting very similar. The guy at my lps said I had a bacterial infection and that I need to treat the whole tank with an antibiotic. Then he said to move them all to my 10 gallon to treat as it’s less water to dose. But when I asked if that means they will just be reinfected once I put them into the big tank he said yes, treat the whole tank. So I’m a bit confused. I’ve read on here that it’s not the best to medicate your whole tank with antibiotics. I’m worried about crashing my cycle and my other corys look very happy and healthy, I don’t want to upset them. Is there any other treatment I can do here? Maybe just move the lethargic ones to the 10 gallon and treat them or am I just going to keep loosing fish if I don’t treat the whole tank? Any advice would be greatly appreciated as I really don’t want to loose anymore corys. The water is 24C or 75F ph6.6 Ammonia 0ppm, nitrite 0ppm, Nitrate 20ppm and a sand substrate. The antibiotic is tetracycline hydrochloride, is that ok for Corys and shrimp? Thanks again

 

Ok, first of all: Antibiotics are unspecific, meaning, they kill beneficial bacteria, too. If they don't the dose was also too low for the bacteria you want to actually treat. Also the use of antibiotics should be restricted to cases when the reason for the disease is clearly identified as a certain bacterium. That's because there are always bacteria in our tanks. Good and bad ones. Your fish surely can be reinfected when moved back. But not because the bacteria are there (that would mean all fish are affected) but because the affected fish have weak immune systems. The last problem with antibiotics is, that people are using them for every little infection, when a good round of several big waterchanges would work as well. Too many uses make bacteria resistant. Just like in human hospitals there are strains of bacteria nowerdays in aquaria that are resistant to all available antibiotics.

Mostly professional breeders and keepers of big expensive fish have good reason to use antibiotics to secure their assets or investments respectively. Using them for 1-2 fish in a home aquarium is like using a nuke to dig a 2x2m hole.

What is your waterchange and cleaning schedule? Especially with cories that are losing barbels this is important to know. Sand can also be rough on the barbels. Fine sand doesn't always mean rounded and smooth. Too much uneaten food on the ground and bacteria film on the surface can be detrimental to cories, the latter when they go to the surface for atmospheric air.
Also interesting would be how your tank is decorated. Are there enough hiding spots? Any other fish, that could stress them?

The picture is also too small to really tell anything. Except that the dorsal is folded down which means the fish isn't doing good.

Otherwise, take a look at the template for sick fish and just fill it out once, so maybe there can be something we all would not see otherwise just from your info and the questions we ask.

Fish Emergency Template | 376562 | Freshwater Fish Disease and Fish Health

 

Thank you for your reply. That is exactly what I was worried about with using antibiotics. They will just wipe out all of the beneficial bacteria too and do more harm than good. I do at least one water change a week of about 20% and gravel vacuum when I do it. I thought the sand was ok as the barbels on my older corys are really long. I have the 6 bronze corys, 5 peppered, 2 leopard, 6 pigmy corys and 3 Kuhli loaches with some ghost shrimp. No one nips and there are lots of hiding places. Do you think I could up the water changes and vacuuming as a better treatment? I ready don’t want to nuke my tank. I’m new to this but my understanding is that bacteria exist in our tanks good and bad and it’s when other factors get out of whack those fish with weakened immune systems suffer? Is that kind of how it works? Thanks again for your help!

 

Hmm..., I see. You might want to do 50% waterchanges 2-3x a week for the next 3 weeks and then do 50% every week, that usually is a good start. That way you lessen the pressure of pathogens to the fishes immune systems. Maybe also add indian almond leaves and/or alder cones, as the tannins are antibacterial (Beware they aren't meds! They are only prophylactics and are just supporting the process.)

There can be a lot wrong that makes the fish get sick: Bad food, stress, little waterchanges... My guess here is, that the leopard cories are kept in too low numbers and those you got extra brought some disease with them. Usually keeping too many different species of cories is not the best idea, especially if one species is in low numbers. They may school together, but in many cases the species with the lowest numbers is gone after some months.

In your place I would just do a modified water change regimen and add tannins and otherwise just observe. Sometimes it's better to let go of the fish affected and let them die with some dignity in the best conditions you can provide, should there suffering be involved euthanasia is also worth thinking about. Sounds cruel, but that way it's actually easier to prevent the other fish from going that same way, too.

In any way, hope I could help and good luck.

 

Ok, first of all: Antibiotics are unspecific, meaning, they kill beneficial bacteria, too. If they don't the dose was also too low for the bacteria you want to actually treat. Also the use of antibiotics should be restricted to cases when the reason for the disease is clearly identified as a certain bacterium. That's because there are always bacteria in our tanks. Good and bad ones. Your fish surely can be reinfected when moved back. But not because the bacteria are there (that would mean all fish are affected) but because the affected fish have weak immune systems. The last problem with antibiotics is, that people are using them for every little infection, when a good round of several big waterchanges would work as well. Too many uses make bacteria resistant. Just like in human hospitals there are strains of bacteria nowerdays in aquaria that are resistant to all available antibiotics.

Mostly professional breeders and keepers of big expensive fish have good reason to use antibiotics to secure their assets or investments respectively. Using them for 1-2 fish in a home aquarium is like using a nuke to dig a 2x2m hole.

What is your waterchange and cleaning schedule? Especially with cories that are losing barbels this is important to know. Sand can also be rough on the barbels. Fine sand doesn't always mean rounded and smooth. Too much uneaten food on the ground and bacteria film on the surface can be detrimental to cories, the latter when they go to the surface for atmospheric air.
Also interesting would be how your tank is decorated. Are there enough hiding spots? Any other fish, that could stress them?

The picture is also too small to really tell anything. Except that the dorsal is folded down which means the fish isn't doing good.

Otherwise, take a look at the template for sick fish and just fill it out once, so maybe there can be something we all would not see otherwise just from your info and the questions we ask.

Fish Emergency Template | 376562 | Freshwater Fish Disease and Fish Health

May I add the antibiotics actual are meand to treat the (possible) infection on the fish.
They don't get reinfected when put back, they reinfect the tank actually when put back.

What are they fed ? Think about adding leaflitter in the tank.

In"hate" the overuse and misuse of antibiotics just as.much as MacZ
Probably cause we as Europeans notice there isn't much of a difference in survivalrate using them or not (cause they are not available here)

 

May I add the antibiotics actual are meand to treat the (possible) infection on the fish.
They don't get reinfected when put back, they reinfect the tank actually when put back.

What are they fed ? Think about adding leaflitter in the tank.

In"hate" the overuse and misuse of antibiotics just as.much as MacZ
Probably cause we as Europeans notice there isn't much of a difference in survivalrate using them or not (cause they are not available here)

Right, when it doesn't work they bring the bacteria back to the main tank, too.

 

It's all about balance.

 

Hmm..., I see. You might want to do 50% waterchanges 2-3x a week for the next 3 weeks and then do 50% every week, that usually is a good start. That way you lessen the pressure of pathogens to the fishes immune systems. Maybe also add indian almond leaves and/or alder cones, as the tannins are antibacterial (Beware they aren't meds! They are only prophylactics and are just supporting the process.)

There can be a lot wrong that makes the fish get sick: Bad food, stress, little waterchanges... My guess here is, that the leopard cories are kept in too low numbers and those you got extra brought some disease with them. Usually keeping too many different species of cories is not the best idea, especially if one species is in low numbers. They may school together, but in many cases the species with the lowest numbers is gone after some months.

In your place I would just do a modified water change regimen and add tannins and otherwise just observe. Sometimes it's better to let go of the fish affected and let them die with some dignity in the best conditions you can provide, should there suffering be involved euthanasia is also worth thinking about. Sounds cruel, but that way it's actually easier to prevent the other fish from going that same way, too.

In any way, hope I could help and good luck.

Thank you so much, you have been really helpful. I really didn’t like the idea of the antibiotics, I think your plan sounds much better. I think you’re right about the leopards too, I leant the hard way not to believe everything they tell you at a pet shop, like all corys shoal together and do my research first. I was trying to get their numbers up but not overload my tank too. It’s hard to get good advice where I am so I really appreciate your help.

 

May I add the antibiotics actual are meand to treat the (possible) infection on the fish.
They don't get reinfected when put back, they reinfect the tank actually when put back.

What are they fed ? Think about adding leaflitter in the tank.

In"hate" the overuse and misuse of antibiotics just as.much as MacZ
Probably cause we as Europeans notice there isn't much of a difference in survivalrate using them or not (cause they are not available here)

I feed them a mixture of frozen blood worms, hikari sinking wafers and some hikari micro pellets. I will add some leaf litter too, thanks.

 

You're welcome. But DoubleDutch is the real Cory-Specialist here. Learned most from him.

You can be lucky to find a real professional in stores, but the chance is... I think it's safe to say only 1 in 50 store employees knows what they're doing and does only care for sales second after the fishes wellbeing. Only found one of these here in my town and we have 7 different stores here.

 

I feed them a mixture of frozen blood worms, hikari sinking wafers and some hikari micro pellets. I will add some leaf litter too, thanks.

Oh, I already see a problem there: Bloodworms are like chocolate to fish. I feed those maybe once in two weeks in small quantities. They can contain bacteria if you don't rinse them after defrosting. Lost fish to that in the past.

Maybe try some frozen artemia, cyclops or daphnia, those have a better ratio of nutrients than bloodworms. Or freeze dried tubifex (They also like them frozen or alive, but tubifex can contain some nasty parasites that can't survive the freeze drying prozess.), just remember to soak them before feeding.

 

Oh, I already see a problem there: Bloodworms are like chocolate to fish. I feed those maybe once in two weeks in small quantities. They can contain bacteria if you don't rinse them after defrosting. Lost fish to that in the past.

Maybe try some frozen artemia, cyclops or daphnia, those have a better ratio of nutrients than bloodworms. Or freeze dried tubifex (They also like them frozen or alive, but tubifex can contain some nasty parasites that can't survive the freeze drying prozess.), just remember to soak them before feeding.

Ok, I will try that instead. I only feed the bloodworms about once a week as a treat but I will cut that back too. Thanks