HELP - My tank is toxic and it is killing my fish... but not my shrimp...

It sure depends on what the chemical is that is in the tank. All I have are some suggestions, no answers. Weird how the shrimp are fine, but fish die.

1) If you think it was some reagent in the test kits then contact the company that made the test kit. Explain that you think that is what happened, and have them suggest a way to remove that material.

2) Activated carbon has a pretty good affinity for many dyes, perhaps some of the color-reacting materials in the test reagents. I do not know, but I would start by running AC in the filter, and changing it out weekly. Also look into all the *zorb sorts of things you add to the filter. Cuprizorb, Phoszorb and others.

3) Even though they seem the same, could the deaths be from different causes?

4) Some ways to disinfect aquarium equipment if you suspect a disease:

Remove and throw away plants. If something is on a plant there is no way to sterilize the plant without killing it. Alternatively you can use any of several materials at very weak doses, keep the plants alive, but not know if you are killing the disease. (Bleach, hydrogen peroxide, Excel, potassium permanganate, other)

Thoroughly clean the whole system to remove all possible organic matter, loose and biofilms. Scrub all surfaces.
Run the full set up with chlorine bleach. One possible dilution is as weak as 19 parts water to 1 part bleach. I would go stronger than this.
Thorough rinse, then run the whole thing with a double dose of dechlor. If you cannot smell bleach that is fine, otherwise 100% water change and run it again with another double dose of dechlor.
Then wipe everything down with rubbing alcohol. Use a tooth brush or other small tool to get into every corner. Air dry, even setting everything out in the sun and rotating it. Rubbing alcohol evaporates.
I understand how Poret might be something you want to save. You might contact the company and see if the material it is made of tends to grab unknown chemicals, and if you can sterilize it against possible disease organisms as I have described. I would throw away all other media. Cheaper to replace it than to have to go through all this again.
I know you can treat gravel, rocks and sand this way (bleach, rinse, rubbing alcohol, expose to sun), but I am not sure about many other substrates. The softer, porous ones might take in some of the chlorine for example, then release it later into the tank.
Driftwood can be boiled, baked or run through the dishwasher (no detergent).
To bake driftwood: Put it in a low oven (250*F) while it is very wet. Bake until it is dry. The steam of the water getting boiled out of it is that thing that kills a lot of disease organisms. You can do this to potting soil, but it can stink. If you can cook it outside that is better.
You can build (very easy) a solar over, and solarize most of the substrate, filter media, driftwood and rocks from an aquarium.

When all that is done wash it all over again, then set it all back up again and run the fishless cycle, but keep some activated carbon in the filter, and keep changing it out just in case some chemical has made it through the process.

On reading through this again, I might add something else. You are looking at changing out the sponge on the thought that it might have something in/on it. There is a way to go that might work or might totally destroy the sponge.
It might pay to do some reading on chlorine first to get a better feel for what it does. Also for what it does NOT do. You will feel better if you read it rather than depending on what some of us might say. Get reliable info, in other words. I might be a bleach salesman needing a commission!

What I find in reading is that chlorine is normally a gas. It has to be tied to a salt to make it easier for us to keep it in a handy liquid form. Whether dealing with chlorine in the laundry, pools or other places, it has one thing most people notice. It smells pretty strong. That is because it comes out of the solution very easily and blows away as a gas. That makes bleach a really handy thing to use. It reacts with almost everything to clean it and then blows away as it dries. When water companies work on things like water towers and want to clean them up after having a few welders walk around in them, the government agencies in charge of our health say to put "x" PPM in and let it set for 12-24 hours.
If bleach is good enough to clean up after a bunch of construction workers well enough for us to drink the water, bleach will have no trouble cleaning your equipment and making it safe to use. It just needs to be rinsed and then let it dry so the chlorine will blow away. Totally dry! If you still smell bleach, dry it some more.

The downside? The bleach may eat up the sponge, but then if the choice is to replace the sponge or TRY to save it, I would try to save it. In a ten gallon tank, a half cup of unscented cheap bleach and soaking overnight will get it all clean. The gravel can be saved as well but it is a real pain to dry gravel. It can be done but a time consuming pain to dry.

Thank you everyone for the thoughtful responses and information...

PlantedRich, do you have a link for that chart from Mardel?
- I don't *think* that an ammonia spike was/is my problem (at the very least not the first time) since the tank water tested at around 6.4 ph. Also, when the first rapid die-off occurred the fish had been in that tank for several weeks living quite happily without a problem. Anyway, I'd still like to have a look at that info.

Well, I guess I will be tearing everything down. I may try to save the poret... I will definitely contact Swiss Tropicals and ask him what he thinks I should do though. If its a no go I will just suck it up and order another sheet.

I think I will also run some carbon and -zorb products in a filter once I get everything back together. At this point it can't hurt to be paranoid.

Thanks again every body

That chart looks clear, but each fish species, and the age of the fish are more or less sensitive to ammonia.

As a general guide keep the ammonia under .25 ppm with water changes and ammonia locking products.
For fish or other livestock that are more sensitive, or fry, keep it even lower.

I do understand that ammonia is in the form of ammonium (NH4) at the low pH in this case, but still, I would try to get rid of it (find the source and correct it, and do water changes) if there was any reading above zero.

Yes, bleach will evaporate, in time (and a fairly short time) if it is exposed to air. Some parts of the aquarium set up are not so well exposed, so run the dechlor once or twice, then finish by allowing any remnant to evaporate.
As an example, when most water companies used chlorine, not chloramine, aquarium keepers could aerate the water for 24 hours and it would be fish-safe. Note the key is to aerate it, stir it, turn it over... so the chlorine was exposed to the air.

Sure hope you figure out what happened!

Update for anyone reading this for information:

I contacted Stephan from Swiss Tropicals (who is awesome) about disinfecting my poret and this is what he had to say:


I am going to do this later today so I'll let you all know how it goes down.