Sick Ranchu Goldfish PLEASE HELP

[ranchulover1101]

This is my ranchu little panda, about 2-3 days ago I began to notice that he had begun to lose what looked like a signficient amount of weight in both his face and belly, in the past couple days he's developed some concerning symptoms like what appears to be very slightly cloudly eyes, the weight loss, a droopy back fin, lethargy and laying down at the bottom of the tank. I would really appreciate any insight into what could be causing this and / or help on treating him

Our tank is 75 gallons with 3 small orandas, little pan and one mid sized Ranchu. We clean this tank about twice a week with a water vacuum, filter is changed out and replaced one a month. The only decorations are some soft plastic plants and rocks. We feed them a diet of peas, broccoli, bloodworms and sinking pellets that is rotated around daily.
I used a API test strip which showed both nitrate and nitrite are at 0 ppm. GH appears to be 30 ish and KH is 240, the PH is about 8.0 - 8.5 in between.

We had bought an additional ranchu 1 month ago but he was very aggressive and harassed the other fish so we had returned him, I don't think we quarantined him iirc. The other fish have been together for about a year now and they all appear to be very healthy and have not had any health issues up until now

My concern is that we previously had two other ranchus who on separate occasions, exhibited the same syndromes as little panda here (sudden weight loss, droopy back fin, lethargy, laying down on the gravel) and eventually died shortly after developing these symptoms. I have not noticed any other distinctive symptoms since there are no lumps, bumps bruises or anything like that, the most noticeable concern I have is the very sudden weight loss and the droopy fin which mirrors the symptoms my other two ranchus had before succumbing to their illnesses.

I can't really think of anything that would stress him out since all the fish get along very well, we don't handle them or anything and we clean the tank pretty often, though im not entirely sure how often we would be ideal for a tank of this size and 4 relatively small fancy goldfish + 1 mid size Ranchu.

Any and all help or suggestions would really, really be appreciated. I've tried looking for illnesses with these symptoms and I'm at a loss for how to treat and help my goldfish

Tank for context

What Little panda used to look like before his weight loss

 

[Autumnsky]

Are you familiar with the nitrification cycle? Article link in my signature has helpful information on using the BB / beneficial bacteria.

I didn't see a parameter for ammonia.

How often do you do pwc and how much do you change?

The cloudy eyes usually is from poor water quality - could be from ammonia.

If you have done a at least 25% pwc in the past week, do 2 more pwc back to back of 25-30%. Then the next day do another one and another the next day.

If you have not done a pwc lately, over 8+ days, then do 15% then another 15% back to back (approximate % is fine).

Wait another 8 hours and do a 25%, then another 8 hours another 25%. Then the next day another 25%.

If you have done a 50% pwc in the past week, do back to back - so 2- 25-30% next day the same, and so a bout 5 water changes.

The idea behind this is a modest change in water parameters, so that the changes are gradual and more gentle, but urgency is also dependent upon the degree of illness of the fish.

If it seems you might loose this fish you might want to speed up the water changes closer in time. It is hard to guess what exactly it is. Getting the water quality in top condition is essential for wellness.

It's certainly possible the bullying fish caused the weakened immune system, maybe illlness, like shared some parasites.

If you have a vac, you might use it to clean up the substrate, as a preventative measure in case of parasites.

Have you noticed the fish's poop? Color, white, stringy?????

I am sorry your cute Ranchu is having these issues. Hoping this can help get him back to health / figure out what is going on.



This will help get a good refresh of tank water in the tank.

Sometimes this is enough.

 

[Autumnsky]

https://www.aquariumadvice.com/fish-disease-index-for-diagnosis-and-treatment/