Dying Tropical Fish

[kartinmartin]

Has anyone had this problem before ?? Tank is 280L with 2 tetrajet 1200 filters and is 5 years old, well maintained regular changes etc, water tests as it has for the last 5 years with no nitrite and approx 35/40 nitrate and run at 80/81 degrees i also have a UV filter, all clean and nice - a slight beard growth on the plants but nothing to worry about.
Variety of fish including Discus, tetra, mollies, swordtails so nothing strange. I have had no fish deaths for months, problem is when i introduce new fish to the tank they die within 5 minutes if it's a tetra or i tried with a discus last night it lasted an hour and slowly faded away, this has been going on for a few weeks, i have changed the filter contents, introduced the UV to try and kill any bacteria 33% water changes using water safe every week, taken out all old plants but still no luck. Last time i tried it with a Discus it was almost dead and i returned it quick to the fish shop and he put it back and it recovered !! all fish have been purchased from the same shop and nothing introduced to the tank except for 3 swordtails for eh last 2 months, when i got the swordtails i purchased 5 to try them and 2 died in 5 minutes and the others lived but they are the only fish out of all i have tried that have survived - any advice

 

[fluttermoth]

What are you using to test the water, and have you tested for ammonia? How many of each species to you have?

Oh, and how long ago (and why!) did you change the contents of your filter?

 

[kartinmartin]

Thanks for getting back to me, i am using a proper master test kit and even the fish shop who is trying to help me solve this has tested the water and says it's fine, there is no ammonia at all in the water its clear, i have mainly pairs of fish although i have 8 cardinals and 6 tetra's, i am not over stocked and these have been in the tank for many months without loosing any of these "originals"

This problem started about 6 months ago when i tried to introduce a new discus and it died overnight, not wanting to try another one i tried a swordtail and that died, after "testing" the tank with various small (and cheap) and getting the same problem we decided to eliminate things that could cause it and one week i stripped and changed the contents of one filter, left it for a week tried a fish and it died so changed the second filter left it again for a week tried a fish and it died, cleaned all the pipes at the same time as the filter, both were changed 3 months ago and have not been touched since, i always wash them out in tank water and not tap water

 

[fluttermoth]

Hmmmm...

There must be something in your tank that your current fish are acclimatised to that's killing the new ones. The normal cause of that is high nitrate (otherwise known as 'old tank syndrome'); are you banging hell out of the bottles of the nitrate test (there's a powder in bottle two that likes to precipitate out)?

 

[kartinmartin]

this is what we have said (me and fish shop man) that whatever it is the others have been introduced slowly and are used to it, i purchased a new nitrate test kit and teh fish man tested it at the shop with his and came to the same level as me around 40 which is the level it has always been, i even tried a nitrite/nitrate mat to help but still the same problem, we thought the UV light would have killed any other bacteria but no change i am at a total loss and even the fish shop man is lost with this one

 

[Fishy friend2]

Sorry if you've already answered this but how specifically are you acclimating the new fish into the tank

 

[afremont]

this is what we have said (me and fish shop man) that whatever it is the others have been introduced slowly and are used to it, i purchased a new nitrate test kit and teh fish man tested it at the shop with his and came to the same level as me around 40 which is the level it has always been, i even tried a nitrite/nitrate mat to help but still the same problem, we thought the UV light would have killed any other bacteria but no change i am at a total loss and even the fish shop man is lost with this one

How do you acclimate them? Do you just put them in, or do you gradually add tank water to their bag in stages over an hour or two? How different is your pH from the LFS? Do you dose your tank with any thing like plant ferts, salt or copper? Do you have plants and/or CO2? Do you adjust your pH? Ever had any major fish kills in the past?

 

[tribalbrit]

Could it be the temperature most shops I believe run their tanks at about 75 - 76 so a sudden shock up to 81 could have an adverse effect.

 

[kartinmartin]

I put the bag in the tank and will only put the fish in the tank when the temperature is the same usually 20 minutes, I don't add water slowly just get the temp right and add them like I have done with all the fish for years with no problem my ph is 6.8 the shop is 7 so should make no difference and there is no additive in the water just water safe on water changes, had no major fish losses just the standard losses you would expect, I checked all hiding places to see if a big one had died without me noticing and rotted away causing problems but nothing and the water was still testing ok

 

[Tizer]

what test kit exactly and what readings are you getting exactly.

 

[ZoddyZod]

the acclimatization method sticks out for me - I understand it's worked in the past but I'd still be looking to slowly add water to the bag oever time before adding the fish.

why not try it with a few inexpensive fish to see what happens?