Mysterious Cory's deaths

[becky412]

I have corys dying. I have a 36 gallon bow front. Had 2 albino and 3 panda. All less than 1 inch big. Also have 2 pleco and about 8 tetras. First the albino disappear, then a panda. Last I looked, I could only find one panda. I was planning on moving 1 or 2 over to my 55 when they got a little bigger. Water parameters are - Ammonia - 0, Nitrite - 0, Nitrate - 10ppm, KH - 2, GH 3, pH 7.4, temp 78 (heated through ambient air temp). All other fish okay. Alternate between feeding flake, bloodworms, tubiflex worms and sinking wafers. I have NEVER had this much trouble with cory's.

 

[Slaphppy7]

How long did you have the corys before they died? What kind of substrate is in the tank? What type of tetras?

 

[becky412]

I had the cory's about 2.5 weeks. I originally had 2 albino bought 8/16/2022. Then one went missing. Since my favorite fish store is 1 hour away (live in rural area), I bought 2 more albino and 2 spotted cory's from my local Petsmart 8/28/2022. They were in a 5 gallon quarantine tank first with 2 other cory's - so 7 in the Q tank for 2.5 weeks. I acclimated appropriately and placed 2 albino cory's in the 36 gallon bow front. So there were now 3 albino cory's. I also transferred 3 panda cory's into this same tank. I had 2 spotted cory's that were a little larger that I transferred into my 55 gallon - they are still doing well.

My substrate is pea gravel.

Both of my tanks are set up exactly the same, same substrate (pea gravel), a mix of live and artificaial plants and decorations for hiding in. Both are running on cannister filters that are set up exactly the same. The temp in the tanks (77-78 degrees) are the same - no heaters are being used. I have 2 power heads in the 55 - one at top of water level and one low along back wall due to length of tank. The 36 gallon has a power head at the water level for circulation. Both have spraybars that are pointing forward and slightly down to help with circulation. Parameters on both tanks are the same.

The only difference are the fish. The 36 bow front has 3 Lemon, 3 Red & Blue Columbia and 2 Von Rio tetras and 2 small (2-3 inch) bushynose plecos (and currently 1 panda that I can currently see). The 55 gallon has 13 quarter to half-dollar size blue angels of different species (yes, I will be thinning them at some point), 2 spotted cory's and 4 small (2-3.5 inch) plecos.

It is a mystery as far as I am concerned.

 

[Colin_T]

I wrote a lovely article about what to do if your fish get sick. The mods were even good enough to pin it to the top of the emergency section. It suggests people provide pictures of the sick fish when they do a post so we can see if the fish have a disease.

No pictures available so now I have to ask my questions, any pictures of the sick fish and tank?

how long have you had the fish?
what symptoms do the fish have?
did you add anything in the 2 weeks before this started?

how long has the tank been set up?
how often do you do water changes and how much do you change?
do you gravel clean the substrate when you do a water change?
do you dechlorinate the new water before adding it to the tank?

 

[becky412]

I wrote a lovely article about what to do if your fish get sick. The mods were even good enough to pin it to the top of the emergency section. It suggests people provide pictures of the sick fish when they do a post so we can see if the fish have a disease.

No pictures available so now I have to ask my questions, any pictures of the sick fish and tank?

how long have you had the fish?
what symptoms do the fish have?
did you add anything in the 2 weeks before this started?

how long has the tank been set up?
how often do you do water changes and how much do you change?
do you gravel clean the substrate when you do a water change?
do you dechlorinate the new water before adding it to the tank?

I have attached a pic of tank.
See my response above regarding acquisition of cory's tanks, water parameters and other tank specifics.
One set of cory's I acquired on 8/18, and another set 8/28.
No pictures, never see sick fish or any symptoms - there one day, gone the next. I have even move plants and decoration to see if I can find them - dead or alive.
Nothing added other than cory's
BOTH tanks have been set up since middle of June, 2022
I do water changes when my Nitrate ppm gets to 30
I do a substrate vacuum about every other time I do a water change - I don't like to do too much all at once which could upset the dynamics of the tank.
Cannister filters have been opened and checked. Sponges and filter media are not in need of maintenance. I have pre-filters on intake.
I use API Tap Water conditioner when ever I add water.

 

[Slaphppy7]

You should be doing weekly WC's, not just when the trAte levels get high...trAtes are harmful to fish at 30 PPM

And TBH, I wouldn't buy fish from the box stores (Petco, Petsmart)...they're rarely in good health

 

[becky412]

You should be doing weekly WC's, not just when the trAte levels get high...trAtes are harmful to fish at 30 PPM

And TBH, I wouldn't buy fish from the box stores (Petco, Petsmart)...they're rarely in good health

Thanks for the info. Everything I have seen from ALL kinds of videos from ALL kinds of professional fish keepers states that <=30 is not harmful or deadly BUT should do a partial. Too much, unnecessary, water change is not good causes stress on fish. And BTW, my water changes tend to be every 10-14 days.

And yeah, I don't like buying fish from big box stores but my options are limited. It is either order and have shipped, which I have, which increases the cost of the fish double to triple, or drive 1 hour one way to a fish store, which is where I purchased my first albino cory's and they have since disappeared. Since I believe in quarantine, I feel that I take an acceptable risk.

 

[Byron]

The advice regarding nitrates is false and dangerous. There is scientific evidence that nitrates do affect all fish. The fish species, the level of nitrate, and the exposure time are factors but the bottom line is nitrate is dangerous. Ammonia and nitrite harm rapidly, but nitrate also harms but more slowly. The issue here is that it weakens the fish so they become more susceptible to whatever. It is proven that nitrate causes hole in the head in cichlids, which are especially susceptible to nitrate. But it affects all fish in some manner.

Nitrates should be as low as you can get them, and then never increase substantially. Regular water changes--once a week, and 50-70% of the tank volume. The biological system is kept stable, or should be; do not rely on tests indicating trouble to do water changes. If this does not keep them low, add floating plants, and increase cleaning of the substrate and the filter. Provided you have no nitrate in the tap water (Have you tested it alone?) then it is the biological system that causes them, and this you can fix. Keep in mind that all the fish we keep in aquaria come from waters with nitrates so low they would not even be measurable with our basic test kits.

My article on water changes is pinned at the top of this forum, link:

Regular Partial Water Changes

Byron Hosking November, 2010 (rev April 2021) Nothing is more important when it comes to aquarium maintenance than regular partial water changes. The adage “an ounce of prevention is worth a pound of cure” certainly applies here. One frequently reads of products that will reduce the need for...

www.fishforums.net

 

[Kyshiara]

The gravel might be to big for them?