I think one of my tanks is cursed.

  • #1
Hey there! I have two fish tanks, one is a 29-gallon community tank that I set up in August. It has been doing great, I had some ich that I successfully treated without losing anybody and I killed my cyle on accident and got through that without losing anybody. I have only lost 1 little fishy who had a parasite. I separated him and put him in a bowl with salt...only to learn later that just keeping him in a salt bowl probably did more harm than good so that was my goof and I know better now. I feel like I have educated myself pretty well on the types of fish I have and what they need to be happy. I watch a lot of youtube and do a lot of research.

So....feeling confident in my fish keeping abilities, I, of course, got another tank. I got it used from my LFS. On Black Friday they had everything 50% off so I walked out of there with a decorated tank on a wooden stand for $25. I emptied the tank and washed it with white vinegar. I added plants, a sponge filter, and a heater. I squeezed my sponge filter from my other tank into it to get the cycle going. Once that was good I purchased a betta. A week later, I got 2 panda corys, waited a week and got 2 more and did that until I had 6. I wanted to add slowly so I didn't overwhelm the tank. For the first month, everything was fine and then everybody died. My parameters were 0 ammonia, 0 nitrite, and less than 20 nitrate. I test both my tanks on Tuesday, Thursday and Saturday and do weekly water changes. The parameters were never bad. But....at this same time, I got some BBA in my 29 gallon and after many hours of searching the internet and consulting youtube, I started treating that with hydrogen peroxide and Seachem excel. (A month later no more BBA and the fish are fine, I even have two amano shrimp in there who were unphased.) I decided to treat the 10 gallon for good measure, but I only did one treatment since there wasn't any BBA in there...but the internet said it can be there before you see it so I wanted to be proactive. Within 3 days all of my panda corys died. The betta seemed okay at first, but he slowly got more and more lethargic over the next month and he didn't make it either. I'm thinking I overdosed my fish and killed them.

From there I got a few mystery snails to keep the cycle going (who are still alive and still super cute). About a week after I put in the snails I got another betta and 3 x-ray tetras. The parameters were good the entire time (0,0, less than 20). The xray tetras lasted about a week and the betta died today. The first time I feel like it was my fault. But this time...I don't know what happened and I'm scared to put anything else in there. I took a video of the second betta (the red one) up to my LFS on Sunday and they gave me a medicine mixture to dip him in. I was told 1 minute a day for 5 days. But no luck. The last picture posted is him this morning. I'm pretty sad about this. Maybe it will just be a snail tank. I also wonder since the tank was used is it possible that there is something in there that the fish are getting sick from? Maybe bacteria or something? 14 fish have died in there.

So I'm looking for advice on this, I have tried to figure it out myself for a while. Thanks in advance!


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  • #2
Hello! Sorry to hear about your troubles. I don’t have any advice for you unfortunately, but wanted to get in on this thread because I’m curious too

  • #3
First of all, sorry this is going on with your tank and that you lost your fish. That mist feel rather discouraging...

Did the first and second betta show the same symptoms? Any heavy breathing? Signs of parasites like velvet for example?
It sounds to me like what killed him might have killed the second betta, too.
Which medication did you use for him? Did you treat the tank with any medication?

I have three possible explanations. Keep in mind I am not very experienced, so these are all theories.
Velvet, gill flukes or something in the tank is leaching toxic chemicals into the water.

Before your bettas got very lethargic, did you notice any rubbing or flicking or erratic swimming? Maybe even weird swimming close to objects or the glass as if he is trying to scratch himself?

Moving forward I would probably nuke the entire tank. Take everything out, thouroughly rinse the tank and all the decorations and equipment with a bleach solution, replace the substrate or rinse it with the bleach solution as well, let it all air dry completely and start over. (This approach would be rather radical but should take care of any diseases that could have been the culprit.)
  • #4
Did I get that right, you only added fiah to that tank, not to the other one you got first?
If so I would almost suspect that you introduced some pathogen to the new tank and/or you only got sold sick fish.

I'd run the tank without fish for at least 2 weeks and then retry with stock from another fish store. After 2-3 weeks most parasites and diseases have died off without a host.
Also maybe try to watch longer before you do anything. It seems you tend to be kinda pro-active.
  • Thread Starter
  • #5
Hello again and thank you for the feedback. To answer RunsOnCoffee...The two bettas both were lethargic and then just stopped. There was nothing physical to see like velvet, fungus or ich. As far as the medication, I used IAL and a little bit of salt in the tank, then my LFS gave me a water solution and said to dip the second one in for 60 seconds a day for 5 days. He died on day 2 and I honestly don't know what was in the solution. I showed my fish guy at the LFS a video of him and we both agreed it looked like he was struggling to breathe. No funny rubbing or swimming until they just looked like they were sick...they looked tired.

To answer MacZ...You got it correct. I have two tanks...one is a community tank and the ones that died were never in there, just the other tank.

I thank both of you for your advice, I think both of you are right, the tank needs a reset.

Again...thank you!
  • #6
Did you rinse the tank really really well? Did rinse the tank really really well after the vinager?
I MIGHT consider removing the fish to a bin with the filter and the heater. the soaking the tank for 10 minutes with a one part bleach to 12 parts water solution. then rinse really well, then let it dry for 24 hours, then add water and dechlorinator.
also what are BBAs?
  • #7
Bearing in mind that the aquarium is secondhand, did the seller give its history before you bought it? Such as what was in it previously, any illness issues etc?

I have come across older used aquariums that "look" fine and I have bought them and had similar experiences to what you are having

Boiling water & Miltons baby bottle sterilising liquid has usually worked for me...and an unused nail or toothbrush

Older aquariums can harbour all sorts of nasties in the silicone sealant, on the glass....and that includes BBA spores that white vinegar can miss

Strip everything out, put your rubber gloves on, half fill with boiling water and Miltons according to dose instructions and scrub it out....use the nail or toothbrush to really scrub the corners and especially around the inside of the base....edges/corners....scrub it to within an inch of its life for about 60 tp 90 minutes. If the aquarium has a top frame use a cocktail stick to rootle out anything that might be lurking in there....do the same for the hood too....leave no surface unscrubbed

Once you have done that pour the water out and repeat 2 or 3 times more before using plain water to rinse all residue out 2 to 3 times. Leave the aquarium upside down on a clean bath towel to dry thoroughly, ideally 24 hours minimum

Do the same cleaning procedure for any ornaments as well

Then start again with your aquascaping and cycle, keep the cycle going for at least 8 weeks before any livestock are added and just add livestock one at a time, once a week and you should break whatever nasty is loitering within that aquarium

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