Goldfish - Tail tips have turned black

[Slaphppy7]

Sounds like disease, maybe septicemia with the shark, but I'm no expert on fish diseases.

Be sure to follow the directions for the API test closely, then post pics of the test tubes here...the directions can be hard to follow (for me anyway), so I made this "cheat sheet" that I use when testing:

AMMONIA:
8 DROPS FROM BOTTLE 1, 8 DROPS FROM BOTTLE 2, SHAKE 5 SECONDS, WAIT 5 MINUTES.

NITRATE:
10 DROPS FROM BOTTLE 1, INVERT TO MIX, VIGOROUSLY SHAKE BOTTLE 2, 2 MINUTES OR MORE, 10 DROPS FROM BOTTLE 2, SHAKE HARD FOR 1 MINUTE, WAIT 5 MINUTES.

PH:
3 DROPS, INVERT TO MIX, RESULTS ARE IMMEDIATE.

NITRITE:
5 DROPS, SHAKE 5 SECONDS, WAIT 5 MINUTES.

HIGH PH:
5 DROPS, INVERT TO MIX, RESULTS ARE IMMEDIATE.


You can run the tests, then post pics of your filled test tubes here.

I would quit using the Aquaria Clear, it's not needed, and adding too many chemicals to a tank can complicate things...see if this water conditioner is available where you live, it's the best out there, IMO, and very economical: https://www.seachem.com/prime.php

[Boundava]

Agree 100% with above. Seems like all the fish died from ammonia poisoning, or septicemia brought on by ammonia poisoning. And just to confirm you had all of those fish in your 80 liter tank? that equates to about 20 US gallons that is too many fish for a 20 gallon tank especially if you have multiple goldfish in there, one goldfish needs 20 gallons, 80 l. That could be why your fish died one by one, there was just too many fish in the tank the filter can't handle that much waste especially goldfish are big waste producers. you would have to be doing a 30% water change every day to keep up with the amount of waste. Also goldfish prefer cooler Waters it suits them metabolism better, in warmer water is the metabolism revs up and so they tend to be hungrier all the time and produce a lot more waste. as it is in cooler Waters you're still supposed to feed them two to three small meals a day something that they can eat within a minute or two. that's just because their digestive systems are linear what goes in literally goes straight out. Then I'll get too much nutritional value out of it as it's running through their GI tract, so you have to feed them multiple times a day. majority of other fish have a more convoluted GI tract so the food stays and their bodies for a longer period of time and the nutrients are able to be pulled out a little bit more efficiently. This is my goldfish a lot more messy tankmates, because they're constantly pooping out what they ate and what they are extreating is still high in nutrients so it tends to dirty the tank faster than say a whole school of tetras eating the same amount and producing the same amount of waste.

[BlueSwan]

These are small gold fishes. The biggest was under 3". They've been around for years...all fishes are small. I've been feeding them alternate day so the tank remains clean. If it's a cumulative incremental effect of this, then I dont know.

[BlueSwan]

Sounds like disease, maybe septicemia with the shark, but I'm no expert on fish diseases.

Be sure to follow the directions for the API test closely, then post pics of the test tubes here...the directions can be hard to follow (for me anyway), so I made this "cheat sheet" that I use when testing:

AMMONIA:
8 DROPS FROM BOTTLE 1, 8 DROPS FROM BOTTLE 2, SHAKE 5 SECONDS, WAIT 5 MINUTES.

NITRATE:
10 DROPS FROM BOTTLE 1, INVERT TO MIX, VIGOROUSLY SHAKE BOTTLE 2, 2 MINUTES OR MORE, 10 DROPS FROM BOTTLE 2, SHAKE HARD FOR 1 MINUTE, WAIT 5 MINUTES.

PH:
3 DROPS, INVERT TO MIX, RESULTS ARE IMMEDIATE.

NITRITE:
5 DROPS, SHAKE 5 SECONDS, WAIT 5 MINUTES.

HIGH PH:
5 DROPS, INVERT TO MIX, RESULTS ARE IMMEDIATE.


You can run the tests, then post pics of your filled test tubes here.

I would quit using the Aquaria Clear, it's not needed, and adding too many chemicals to a tank can complicate things...see if this water conditioner is available where you live, it's the best out there, IMO, and very economical: https://www.seachem.com/prime.php

Thanks for that! I'll post the results over the weekend, prior to doing the water change.

This particular fish from the original post seems to be acting normal and doing just fine. The pattern on it's tail is highly symmetric. Could it be a normal pattern that is now appearing to whatever response to the environment? Not that anything has changed for him, but still...

[Slaphppy7]

I do think it's just natural coloring.

Great advice above from Boundava, as well.