Help! Everything in my tank keeps dying after getting cardinal tetras (TW - Dead fish pic)

[lukesfishies]

I agree with @seangee and advise you to do a 75% water change and vacuum the gravel. Guppies are more hardier than cardinal tetras so there may be something in the water affecting them more than the guppies. Try to always wash you hands before feeding or putting them into the water. Have you added anything to the water like stress coat or anything else?

No I haven't added anything except for water conditioner and some fertiliser a week ago. Should I get some stress coat?

 

[JuiceBox52]

No I haven't added anything except for water conditioner and some fertiliser a week ago. Should I get some stress coat?

Stress coat is actually not good for the fish so I would say no

 

[FishGuest5123]

No offense, but that’s bologna. I love Stress Guard. This site is against it but resources I have asked in aquatic research have said Studies have shown the aloe is not an issue and it’s better than Prime. My bettas have proven that by their tails healing and looking beautiful now. Anyway, have you treated for intestinal worms? Have any of the fish seemed bloated? Swim bladder would not be affecting them all like that do you can rule that out.

 

[Retired Viking]

Sorry for the questions but we are trying to eliminate possible causes, Have you tested your water for ammonia lately? What type of fertilize? Do the cardinals seem better since you did the water change or not? It may be that the cardinals were infected with something before you bought them.

 

[Retired Viking]

No offense, but that’s bologna. I love Stress Guard. This site is against it but resources I have asked in aquatic research have said Studies have shown the aloe is not an issue and it’s better than Prime. My bettas have proven that by their tails healing and looking beautiful now. Anyway, have you treated for intestinal worms? Have any of the fish seemed bloated? Swim bladder would not be affecting them all like that do you can rule that out.

I was asking a general question about what was added and using stress coat as an example, not attacking it

 

[FishGuest5123]

I was asking a general question about what was added and using stress coat as an example, not attacking it

No, it was JuiceBox52 who said it.

 

[lukesfishies]

Sorry for the questions but we are trying to eliminate possible causes, Have you tested your water for ammonia lately? What type of fertilize? Do the cardinals seem better since you did the water change or not? It may be that the cardinals were infected with something before you bought them.

I've checked for ammonia quite a few times and it's at 0. The fertiliser is API leaf zone (not actually fertiliser I know ) and I put it in every Thursday. I haven't changed the water with the cardinals yet as they've only been in there for 3 days,but I'll do one today. The cardinals don't show any other symptoms, they're not bloated and don't swim weirdly until death. The one I was talking about yesterday didn't die and noone else died either since yesterday night (just under 12 hours) so we're at 3 deaths still

 

[lukesfishies]

I haven't treated for worms but they don't seem bloated at all and I opened the dead one up, and despite the horrible smell it didn't seem to have worms

 

[lukesfishies]

Another one seems on its way out now

 

[lukesfishies]

Ah **** I just saw last night's one dead on the floor of the tank. No symptoms on the corpse, just a bit pale

 

[lukesfishies]

Here's another pic of the one on his way out. He's in a Pyrex bowl because they usually die soon after being at a 45 degree angle

 

[Byron]

I am certainly no disease expert, but I would offer the suggestion here that the cardinals may have carried an internal protozoan. If this is the case, and I have twice dealt with this and got advice from a marine biologist at the time, the best action would be to medicate their food with metronidazole for 10 days. It takes a few days for this antibiotic to become effective (just as in humans) so a few more fish may succumb if this is the issue, but it will deal with internal protozoan. Adding it to the water is much less effective. Seachem's MetroPlex is what I have twice used.

Seachem - MetroPlex

www.seachem.com

This is safe for fish. One should never use antibiotics without reason of course, but here I would say it is likely the issue.

 

[Retired Viking]

Sorry about your fish, I hope you are able to save some of them. I would follow @Byron advice.

 

[Essjay]

Unfortunately the OP is in the UK and metronidazole is not available here without a prescription. A vet may be willing to supply a prescription, though there aren't many that deal with fish.

 

[seangee]

I am certainly no disease expert, but I would offer the suggestion here that the cardinals may have carried an internal protozoan.

This did occur to me last night after we seemed to have ruled everything else. Sorry I had to sleep and I'm only just in from work.
Since you (@lukesfishies) are in the UK antibiotics are not available without a vet's prescription. An alternative solution would be to add 1 heaped tablespoon of aquarium salt (not marine salt you just want plain NaCl with no additives). Keep it in the tank for two weeks. Do your regular water changes and replace the correct amount of salt for the water you replace. After 2 weeks just continue water changes as normal.

Edit: Sorry that's one tablespoon per 10 litres of water.