Betta with fin rot?

Good evening and hello - first post here and alas a desperate one. (first tank, first two fish so excuse the possible silly questions)

On Monday got first fish for tank, a betta and bristlenose pleco. The betta I had originally seen and reserved the woman at the shop would not let go due to all fins being clamped and generally looking unhappy, but instead I took another which I was told had had its fins nipped a little but looked well.

Yesterday (Tuesday) I saw a white cotton wool looking spot on one of his smaller fins near the front of his body, and he had been lounging around at the bottom of the tank in the morning and behind the filter (assumed just adjusting). Today, he pretty much has very little tail fin left. His colouring has changed and looks faded, he is not doing very much swimming at all and is sitting mainly on the bottom of the tank. He has gone up a little, but seems to be carried around the tank by the water not by his swimming and I have seen a few times him essentially nose dive and hit the gravel. It looks as though he is breathing deeper than he was yesterday, and it looks pitiful to watch.

I have added aquarium salt yesterday as recommended when I got him, and a fin rot treatment. On seeing him today, I rang a couple of aquarium places and have been told -

- fin rot treatment may have sped up the progression of the issue hence the large piece of tail that has vanished
- do a 25% water change as ammonia level was at 0.2, other water parameters were okay as per dip test and use tap safe
- add some fluval cycle as the medication has wiped out the bacteria in the tank as it wasn't established enough to handle it

I have done the above, turned the light off so as to try and minimise stress but I am so very worried. What else can I do? Im shocked things have progressed as quick as they have done, and feel very helpless and guilty to think I may have made it worse by trying to make it better.

I will try and attach a picture of him on Monday and today so you can see what has happened.

Any advice at all would be welcomed, it is so sad to not be able to do anything other than keep periodically checking to see if he is still alive?

Sorry forgot, parameters prior to 25% water change were -

Tank size: 50l
pH: 7.5
ammonia: 0.2
nitrite: 0
nitrate: 50
kH: 10
gH: 8
tank temp: 27 degrees C

Monday -


Tuesday -


Today -

Hi and welcome to the forum

Take the fish back and get a store credit for another fish but don't get another fish yet.

Do a 90% water change and gravel clean the substrate. Make sure any new water is free of chlorine/ chloramine before it is added to the tank.

Keep feeding down to 2 times a week and do a 75% water change and gravel clean the substrate 4-8 hours after feeding the fish.

Do a 75% water change any day you have an ammonia or nitrite reading, or a nitrate reading above 20ppm.

When the tank has cycled get another fish.

The tank had been set up for weeks whilst the filter cycled and I had been checking the water regularly to see where it was with things - the Betta was reserved but was pending the water quality because this is exactly what I was trying to avoid. It was tested on Sunday and Monday morning before going to get them and the levels were reading “ok” and “safe” as per the back of the test kits.

All I want to know is what has happened so I can avoid this again in the future - was the fish already sick from the shop with the raggedy fins or has something changed within the tank very quickly?

Nothing much to report on him this morning, he’s still lingering by the filter at the top but I won’t stare in there too much incase an audience is stressful.

I won’t lie, it’s disheartening to have tried to set it up optimally which as far as I was aware and the guys in the shop I had done but confidence is knocked!

Thank you Colin for the help, at least there’s something I can do

How did you cycle the tank? Did you just let it run or did you add ammonia following the instructions in the method on here?

I added ammonia to it and kept as close a track as I could with the water tests and strips to see where it was within the cycle so I could make note of it all

So, to update -

Yesterday lunchtime my betta passed away.

Today -

Pleco had ventured out for one of the first times since he and the betta were introduced to the tank. He has had algae wafers and courgette on offer but had not been seen eating anything. His move was stressful as the woman in the shop had to detangle his bristles from the net twice to get him and it was lengthly and I would imagine, unpleasant for him.

At around 4pm he was on the glass at the back of the tank by the filter, with his tail bent on the substrate. I thought he was dead from the odd angle, but he very speedily swam away. Fast forward a couple of hours later and his stomach was very swollen and he was laying on his back under his bogwood trying to suck onto it but his stomach was preventing him. I went to go and cook a couple of peas in the event he was constipated, and get another piece of courgette in the event he wanted that. In the matter of speaking to my dad on the phone about my concern for him and getting the food (in all about 40mins) I can back to see him briefly swimming upside down (all over the place, really) and resting under the bogwood. He sat by the bogwood and died.

Could whatever my poor betta had (finrot) have killed him too? if not, what else could cause this?

We went to the place they were purchased from yesterday to tell them and we saw that several of the other fish had noticeable fin rot.

I am so sad and disheartened. Now I have an empty tank with no idea how to proceed from here

The pleco ballooning up (getting really fat suddenly) is normally caused by an internal bacterial infection. When you feed fruits/ veges to fish, make sure they are free of chemicals and wash them well. It you can peel the skin off the fruit/ veg it is better because it reduces the chance of anything being on the skin that could contaminate the water.

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If you don't have any fish left then flush the tank out and wash everything under tap water. Then fill it with tapwater and add a heap of salt. Add any sort of salt until it no longer dissolves and then add more. You want a layer of salt on the bottom of the tank.

Get the filter running and leave the salt in the water for 24 hours. Then drain and refill the tank a couple of times. Wait a few days and add 1 cheap fish, probably a Betta if you want one, (do not get a catfish, loach or eel). Check the fish for fin rot, spots, patches or anything else. If it isn't perfect, don't get it. If you have any concerns or the fish doesn't look right, don't get it. Possibly even check out another pet shop instead of returning to the place you got the other fish.

Some pet shops give you a replacement fish if you take the body back within a few days of buying it. You can ask the store if they are willing to give you a replacement Betta due to the original one dying from fin rot/ bacterial infection, and the catfish ballooning up. They might tell you to get stuffed or they might give you another fish. If they tell you to get stuffed then find another pet shop.

When you get the new fish you will be doing a fish in cycle. During this time you only feed it 2-3 times per week and do a 75% water change and gravel clean the substrate 4-8 hours after feeding. You should monitor the ammonia and nitrite levels and do a 75% water change any day you have an ammonia or nitrite reading. When the filters have settled down and established you can feed more often and do a water change each week.
Make sure any new water is free of chlorine/ chloramine before it is added to the tank.

Use clean buckets that have not been used for anything except the fish.

If the new fish has any issues, test the tank water for ammonia and nitrite and post pictures asap. If the fish has the same problems as the last ones you will need to bleach the tank, but don't do that yet.