What killed my betta? Should I disinfect my tank?

RedSarah

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Hi all!

Something I've grown to accept is that this hobby can be as distressing as it is gratifying. In my limited experience, I've found that the fragility of the artificial ecosystems we create means that the state of a fish or a tank can turn abruptly. I’m usually here with questions and fish emergencies, and I’d like to rectify that and post about my planted tanks and healthy fish! But, unfortunately, I did not have the chance to post about my newest betta.

I guess I’m here to ask you for your thoughts and to use this as an opportunity to learn from any mistakes I made so that this doesn’t happen again. I’d also like to know if I should somehow “disinfect” my tank to prepare for when I’m ready to get another fish.

I only had Remy for two months. He came from a reputable American betta importer who is popular on Instagram. He arrived to me in beautiful form—fins extended, color vibrant, and with curiosity and energy. He was a beautiful super red HMPK, with a handful of pink iridescent scales near his tail. I have two nano tanks and Remy was my only fish. I really wanted to apply everything I’ve learned from this forum over the last few years, and from my past fish, so that he could live a long and healthy life.


SETUP

Tank size: Planted, cycled 7 gallon cube (26.5 liters)

Filtration and heater: Internal filter with mature media, and a heater set to 80F (26.7C)

Tank mates: 1 nerite snail

Diet: Omega One pellets, NLS pellets, Bug Bites soaked in tank water/Freshwater Vitachem. Hikari frozen foods as “treat” meals a few times a week.

Water changes: 40-50% once a week with temperature matched tap water (7.4 pH) and Prime.

API Liquid test kit bi-weekly, or if there is a problem in the tank. Params are:
Ammonia: 0ppm
Nitrite: 0ppm
Nitrate: 5ppm
kH: 5 dKH
gH: 9 dKH

Additives: NilocG ferts ("liquid carbon", liquid NPK, and micros), add each once a week at half the recommended dose


About two weeks ago, Remy seemed skittish after a water change. I figured I had just startled him at some point because he seemed better the next day. I’m not sure if this was a precursor to the following issues, but he did seem a bit less active for the remainder of the week.

On Saturday 12/19, I noticed Remy had nicked the end of one of his ventral fins. When I got home from work, I checked on him and prepped to do a water change for his injured fin. He was hanging at the top of the tank (not gasping), fins slightly clamped, and was twitching when he swam. I looked closer to check his fin injury and noticed a tiny stream of blood sort of dissipating into the water, which seemed to be coming from his gills. It stopped quickly, but I do not know how long this had been going on while I was at work. I immediately tested the water with API liquid test kit and got:
0ppm ammonia
0ppm nitrite
5ppm nitrate

I performed an 80% water change because I was concerned about contaminants in the tank (I’ve read the posts about hand sanitizer poisoning, though I wash my hands thoroughly with hot water before maintenance and feeding). He showed little improvement the next day, but had developed a tiny fluff of fungus on his injured ventral fin. My understanding of fungus is that it’s opportunistic and usually affects fish if they are weak or stressed. He was still eating eagerly and color was good, though his chin and gill plates looked slightly pale/grey.

I was set to drive to my parents house on Monday for Christmas. So, I performed another smaller water change on Sunday and added aquarium salt to the tank to try and combat the fungus until I could get back home. I have a great petsitter who was scheduled to come by to feed and check on Remy every few days. I set up my cat camera in front of the tank. When the petsitter visited on Wednesday, she sent me several pictures of Remy and he appeared to be in the same condition as when I left. Still colored up, but with a pale belly/chin and hanging at the top of the tank. She just dropped his pellets in and they sank to the bottom, so I scheduled an extra trip the next day and asked her to really try and get him to eat. When the petsitter arrived the next day, she found that Remy had passed away and was at the bottom of the tank.

I rewound the pet camera recording and found that about two hours after the petsitter left on Wednesday, Remy began swimming erratically and thrashing, then sort of floating, then thrashing, then floating. This continued for about 30 minutes, until he settled at the bottom of the tank where she found him the next day.



I am nervous to eventually get another fish for fear that something was wrong with Remy’s environment and that this will happen again. I don’t know if I need to sanitize the tank or if this was some kind of non-communicable problem that Remy had. My only thoughts are that:
  1. This is the tank that my last betta inhabited, and she was sick for several months with stubborn fin rot. This could have been age, or a cancer/immunity issue, because she did not improve with any treatments I tried. Though, she declined for months and I ended up deciding to euthanize her, whereas Remy passed fairly suddenly. Tank was empty for about three weeks before I got Remy, and I kept it cycled with Dr. Tim’s ammonia and water changes.
  2. I put those flexible magnesium plant weights on a few of my buce about three weeks ago. I read that they are non-toxic, but I removed them when Remy started acting off. One looked like it had eroded since I put it in the tank and tiny pieces had crumbled off and were on the substrate. They came from my LFS.
  3. I added plants from Buceplant the day before Remy arrived. I rinsed them thoroughly, soaked them all in a diluted hydrogen peroxide bath for about 10 minutes, then rinsed them again. Still ended up with limpets lol, but could the plants have carried some kind of pathogen?

Thanks so much for bearing with me and reading this long post! I feel terrible that Remy was only with me for two months even though I gave the little guy my best fish-keeping efforts. If anyone has any ideas, I would really, really appreciate your thoughts :)
 
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I doubt he died from something contagious. Bleeding from the gills could be from physical damage or a tumour/ growth that ruptured. However, you can usually see gill tumours growing out from under the gill cover. The fish might have eaten something sharp that damaged its mouth or gills and lead to an infection that killed it. Short of getting the fish necropsied (animal autopsy), I doubt you will know the actual cause. But I don't think it was a disease that caused the bleeding from the gill/ mouth/ throat area.

As for the tank, I would wash it all out with water and let it dry. Then set it up and start again.
 
Remy's conditions seem good, you did everything to give him a healthy home and diet.
I don't trust liquid carbon, plants generally have enough in the water so maybe give this a miss next time and see if your plants still thrive?
Sorry for your loss.
 
I'm sorry for your loss.
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I'm with @Colin_T on draining and cleaning the tank and starting over....and that includes the filter and all new filter media.
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Also, most of what is referred to as liquid carbon is really a chemical called glutaraldehyde, which in a slightly stronger form is used to STERILIZE heat sensitive medical and dental equipment! It kills algae and some plants and can't be good for fish. I wouldn't use it!
 
Thank you all so much for the advice. I'm going to drain and restart the tank (and ditch the glutaraldehyde) like you've suggested—I guess this is a good opportunity to get some new hardscape and substrate. Happy New Year!
 
Always be super careful at what you add to your tank. Remember that chemicals of any description can't be good for fish.
 

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