Can Ghost Shrimp kill Cory Cats??

[jonatheber]

I have a 46g bowfront with a bunch of livebearers and (until 2 days ago) 3 cory cats. The water is 33% changed weekly, and has 0 ammonia and nitrite, and 20ppm nitrate. The corys have been fine for months. I purchased a few ghost shrimp to try to help out with some cleaning of the tank (e.g. hair algae) and 5 cardinal tetras to try to brighten up the bottom 1/3rd of the tank. The cardinals all died within a few days - I have high pH, and that probably did it. 48 hours later, overnight, all three corys died. There are no signs of any distress from any of the mollies or guppies or the lonely painted glass tetra in the tank.

Is it possible that somehow the ghost shrimp killed the corys??

 

[Byron]

The shrimp would only be responsible if they introduced something (disease), not by any physical issue or so I would think. The sudden death of th cardinals (new) might be the same, brtinging disease that spread to the cories. The cardinals themselves might be weak fish, but unless that is some pathogen that spread, not in itself likely to have killed the cories.

You mention high pH...when posting about an issue, always give test results for as many factors as you can. None of us knows what "high pH " might actually be...in my soft and acidic water tanks a "high pH" would be anything above 6.5 but that is very low to someone with a normal basic pH of say 7.5 or 8. The pH is important, but so is the GH, do you know that? What is the temperature?

The ammonia and nitrite at zero is good. Nitrate at 20 ppm is close to being high but should not kill so fast, but it is higher than I would want to see it for soft water fish like cories and cardinals. Is this normal? Is nitrate in the source water to begin with? If not, and this is solely occurring within the tank, the easy answer for this one issue is to do more substantial water changes. At least half the tank volume, up to 2/3, and once a week. If this does not lower it on a permanent basis, look at feeding (fish do not need anywhere close to the amount of food all manufacturers will recommend, and missing a day or two or three each week is more benefit than harm (except fry which need more regular feeding). Of the stocking may be pushing things as these fish grow...mollies are not small fish and they do process a lot of waste since they are omnivorous with an appetite for green foods.

Is the substrate vacuumed at the W/C, or are there live plants? And is the filter kept well rinsed? The less organics that accumulate in the filter and substrate, the less ammonia to nitrite to end up as nitrate.

BTW, livebearers must have hardish water, mollies particularly. If they have been doing well, the GH may be OK for them (your number will confirm) but cardinals might find this too hard too rapidly. This caution is now for future fish, but again we need to know the GH and pH.

 

[jonatheber]

The shrimp would only be responsible if they introduced something (disease), not by any physical issue or so I would think. The sudden death of th cardinals (new) might be the same, brtinging disease that spread to the cories. The cardinals themselves might be weak fish, but unless that is some pathogen that spread, not in itself likely to have killed the cories.

You mention high pH...when posting about an issue, always give test results for as many factors as you can. None of us knows what "high pH " might actually be...in my soft and acidic water tanks a "high pH" would be anything above 6.5 but that is very low to someone with a normal basic pH of say 7.5 or 8. The pH is important, but so is the GH, do you know that? What is the temperature?

The ammonia and nitrite at zero is good. Nitrate at 20 ppm is close to being high but should not kill so fast, but it is higher than I would want to see it for soft water fish like cories and cardinals. Is this normal? Is nitrate in the source water to begin with? If not, and this is solely occurring within the tank, the easy answer for this one issue is to do more substantial water changes. At least half the tank volume, up to 2/3, and once a week. If this does not lower it on a permanent basis, look at feeding (fish do not need anywhere close to the amount of food all manufacturers will recommend, and missing a day or two or three each week is more benefit than harm (except fry which need more regular feeding). Of the stocking may be pushing things as these fish grow...mollies are not small fish and they do process a lot of waste since they are omnivorous with an appetite for green foods.

Is the substrate vacuumed at the W/C, or are there live plants? And is the filter kept well rinsed? The less organics that accumulate in the filter and substrate, the less ammonia to nitrite to end up as nitrate.

BTW, livebearers must have hardish water, mollies particularly. If they have been doing well, the GH may be OK for them (your number will confirm) but cardinals might find this too hard too rapidly. This caution is now for future fish, but again we need to know the GH and pH.

Byron - thanks for the detail. I'll try to add as much information as I have.

The pH of the tank is 7.6-7.8. I don't have any way to measure the GH. Is there a recommended test kit for that? The temperature is 78-78.5 degrees. I am positive that the water here is considered "hard" based on all the feedback locally from LFS and others. I just don't know HOW hard.

I'll try a more significant water change. I just did one a few days ago, so don't want to overdo the changes (unless turning it over again so quickly isn't viewed as dangerous).... I do note that I have a live planted tank and use Thrive (the regular one). I don't know if that is leading to the nitrate buildup or not. When I do a water change I use a vacuum - my means of doing the water change is the python hose setup.

I have a Fluval 407 canister filter that I have stuffed with pot scrubbies. I actually did a fairly good rinse of the scrubbies about 2 months ago, even though the recommendations here vary between "rinse them" and "never rinse them."

I have a gravel b

 

[Byron]

Byron - thanks for the detail. I'll try to add as much information as I have.

The pH of the tank is 7.6-7.8. I don't have any way to measure the GH. Is there a recommended test kit for that? The temperature is 78-78.5 degrees. I am positive that the water here is considered "hard" based on all the feedback locally from LFS and others. I just don't know HOW hard.

I'll try a more significant water change. I just did one a few days ago, so don't want to overdo the changes (unless turning it over again so quickly isn't viewed as dangerous).... I do note that I have a live planted tank and use Thrive (the regular one). I don't know if that is leading to the nitrate buildup or not. When I do a water change I use a vacuum - my means of doing the water change is the python hose setup.

I have a Fluval 407 canister filter that I have stuffed with pot scrubbies. I actually did a fairly good rinse of the scrubbies about 2 months ago, even though the recommendations here vary between "rinse them" and "never rinse them."

I have a gravel b

On the GH, se if this is posted on your water supplier's website. No need to test the tank water, it will be the same unless something in the tank is affecting it. Is the gravel inert, or calcareous?

The pH itself is not a problem for cories, the cardinals depend more on the GH.

Water changes are never harmful unless the parameters are substantially different. Temperature close is easy enough, the GH should be the same, and the pH not likely to change much. Fresh water is always going to benefit, so aim for a larger W/C volume.

Thrive plant fert...here is a link to their page, which one are your using? I want to see what is in it, as it may be an issue here.
Thrive All in One Liquid Fertilizers for Aquarium Plants | NilocG Aquatic Labs

If brown gunk is accumulating in the filter media, that is organic matter and best removed regularly. I rinse my filter media every water change. With live plants the filter's only real benefit is water movement, not biological filtration which the plants handle better.

I'll be back online tomorrow to check in and continue.