Can't keep corydoras

[ArtistGardener]

I can't seem to keep corys alive. All of the other fish look great. I use the same method to transfer them from store to tank as the others. I gently pour/slide the bagged fish in their water into a plastic container I keep for this use; I then float the container in the tank with lights off or dimmed; I squirt small amounts of tank water into the container over 45-60 minutes from a bulb syringe. Once the container contains at least half and half water, I remove some of it with the bulb syringe and continue adding tank water. Only when I know the water is mostly tank water do I net or hand lift them to the tank (none of the store's water goes in my tanks). They always look good for a few days, then I find them dead with no physical signs of damage. I currently have three skunk corys. I bought three, lost two within 24 hours; got those replaced, and have lost another within three days. Previously, I lost all of my corydoras habrosus (dainty cory) in my 20 gallon planted tank, too. Is my ph too high? Is it the Excel? Why are my other fish so healthy and unaffected (including otos)? The second time I got the replacements, I extended the acclimating time to two and a half hours.

Ammonia: 0
NitrIte: 0
NitrAte: < 5 (I would like to get this up to help with algae issues, by the way)
pH: 8.2
GH and KH both vary with our tap water over time, but are generally high at 12-14
Filters are two HOB AquaClears at each end of 55 gallon tank--one 70 and one 20.
Temperature is 76-78.
Substrate is Flourite topped with one inch layer of rounded red flint gravel.
Planted tank with driftwood. No CO2 injection, just recommended amount of Excel each day.
Other stock includes 4 otos, one SAE, 8 pristella tetra, one clown pleco.

 

[Kristian Tombs]

PH won't kill a fish usually if it's acclimated properly. Try drip acclimation. Maybe try a different fish store

 

[ArtistGardener]

I am basically doing drip acclimation, but it might be more like a teaspoon, rather than a drip at a time. Do you think an hour is too short? I have purchased fish from three different places and had the same problem---and they looked good in their tanks before I bought them.

 

[GodFan]

Do you add salt? Do you feed any frozen food and if yes what?

 

[ArtistGardener]

GodFan, I do not add aquarium salt. I feed frozen brine shrimp as a treat only two or three times a week. Most of that is gobbled up within minutes.

 

[GodFan]

GodFan, I do not add aquarium salt. I feed frozen brine shrimp as a treat only two or three times a week. Most of that is gobbled up within minutes.

That is why you have dead cories! Stop feeding brine shrimp immediatly! If you have any cories left you need to change your water ASAP! Cories are incredibly sensative to salt and brine shrimp are salty! Any frozen food you feed your cories must not come from a creature that lives in salty water! The reason I know is I killed a bunch of cories with frozen prawn eggs before I figured it out!

 

[ArtistGardener]

GodFan, I appreciate your advice, but it can't be true. If I fed them any time even remotely close to their deaths, I would heed this advice, but the last two attempts at corys didn't coincide with ANY feeding of brine shrimp. One was dead within 24 hours and hadn't had shrimp--and no shrimp had been in the tank for days. I do 25% water changes weekly and feed the tiniest amount of shrimp--always melted in a shot glass of tank water. The bottom feeders never even get any of it as the tetras and other mid-tank and surface fish gobble it up before it even sinks. If by some miracle a few sank and were eaten, the salt in these would be negligible.

 

[GodFan]

GodFan, I appreciate your advice, but it can't be true. If I fed them any time even remotely close to their deaths, I would heed this advice, but the last two attempts at corys didn't coincide with ANY feeding of brine shrimp. One was dead within 24 hours and hadn't had shrimp--and no shrimp had been in the tank for days. I do 25% water changes weekly and feed the tiniest amount of shrimp--always melted in a shot glass of tank water. The bottom feeders never even get any of it as the tetras and other mid-tank and surface fish gobble it up before it even sinks. If by some miracle a few sank and were eaten, the salt in these would be negligible.

It is not the salt they ingest it is the salt that dissolves in the water. You may have a slight build up in the tank from all of those feedings. Of course I could be wrong but it sounds like everything else is right so what else could it be?
I would try to put cories in after either a couple of months without the shrimp or after several huge water changes. Then try and see how long they last with no shrimp.
Obviously it is up to you but unless you have something in your tank harrassing them to death I would say 99% the brine shrimp are killing them.

 

[ArtistGardener]

That's what I mean. The salt in a tiny half cube (about 1/4 tsp) of brine shrimp put in a 55 gallon tank two or three times a week (that gets a 25% water change weekly) would be so negligible you couldn't measure it. I am hoping someone with 1) very hard, alkaline water, 2) who uses Excel for liquid carbon, and 3) has kept corydoras for years responds. I used to have corydoras when I lived somewhere else. My pH there was more like 7.6-7.8, I didn't have live plants so no Excel, and my corys were fine. I fed my fish, including the corys, brine shrimp regularly. It still may be some issue with the length of the acclimation. Maybe I need to do it for six or eight hours. I am just afraid of even more stress to them doing that. All three of the fish retailers I use have regular city water in their tanks (not R.O) except for the discus tanks, so it should be similar to my water. I hate mysteries that involve death of my fishies!

 

[GodFan]

That's what I mean. The salt in a tiny half cube (about 1/4 tsp) of brine shrimp put in a 55 gallon tank two or three times a week (that gets a 25% water change weekly) would be so negligible you couldn't measure it. I am hoping someone with 1) very hard, alkaline water, 2) who uses Excel for liquid carbon, and 3) has kept corydoras for years responds. I used to have corydoras when I lived somewhere else. My pH there was more like 7.6-7.8, I didn't have live plants so no Excel, and my corys were fine. It still may be some issue with the length of the acclimation. Maybe I need to do it for six or eight hours. I am just afraid of even more stress to them doing that. All three of the fish retailers I use have regular city water in their tanks (not R.O) except for the discus tanks, so it should be similar to my water. I hate mysteries that involve death of my fishies!

Well there isnt much I can do to help you then. Excel will not hurt them unless you arent dosing correctly. Water params should be fine and a 1 hour drip acclimation is more than enough. I think it is the brine shrimp. They live in water with more salt than full marine water. Cories are sensitive to the salt even in small quantities. Of I was givin the same advice as you I would at least try it. Its not like its gonna hurt anything or be all that inconvienent.

 

[ArtistGardener]

I will certainly try, but like I said, I had this problem without shrimp being given. Earlier in a 20 gallon, I lost all of my corydoras habrosus (four of them) within a week or so and I had never fed shrimp in that tank at that point. Do you have experience with more than one species of cory? If so, have you noticed some species to be more resilient than others?

 

[ArtistGardener]

Something just occurred to me. I use tap water, adjusting hot and cold to match the tank temperature, which means I am using some conditioned water. I use a dechlorinator, of course, too. Is there enough salt in "softened" water to do this? Could this be it? I know a very tiny amount of salt can show up in softened water. That is another major difference from my old tank years ago--we had a private well and did not soften/condition our water.

 

[GodFan]

I have had experience with a few. To me they all seem resilient. And yes the water softener could definetly do it. I still wouldnt feed the brine shrimp but the water softener is probably your cause of death!

 

[molliwopp]

Also try buying your cories elsewhere! Bad stock happends.

 

[ArtistGardener]

In the process of doing a major water change with non-conditioned water. I hope this fixes the problem! Thanks for your help.

 

[GodFan]

Hooe so too!

 

[azmodan]

Do you buy them all from the same store? Any chance you know the store's ph and how long they've had their stock before selling them? Any signs of disease when they are dead? When you put them in do you turn the lights off? Any possible bullying by the tetras? Just trying to hit all possibilities.

 

[20cc]

Also try buying your cories elsewhere! .

 

[ArtistGardener]

Thanks, Azmodan, but if you read my initial post you'll learn that I have bought from three different stores, all looked great when I bought them. This last group was in a tank at the store for over two weeks with no new additions. I don't know the pH at the stores, but have been told they are using straight city water (our area has rather high pH) with no RO water in the mix. I acclimate over 45 minutes to several hours, as well, with partial water changes. The tetras are not bullying--there are no visible signs of damage whatsoever, other than pinkness around the gills. I am thinking that GodFan is right and it relates to sodium (but not from food, it may be my water).