Hi there and welcome to the forums!

May I ask how big the normal tank is that Dory normally lives in? How many other fish are in that tank? How often and how much do you do water changes?

Red veins in the tail can suggest either poor water quality or a bacterial infection, where the fin is ripped, is it a clean slice or is the fin deteriorating?

Hope the fish is doing okay, we will do our best to help you!

Okay, so that's 65 gallons then? Which is... around 290 litres...
I can also see, you have fancy goldfish and single tailed goldfish together... I would normally suggest for a tank like that to only keep fancy goldfish (3 or 4 would be plenty).

Normally single tailed and fancy varieties of goldfish aren't kept together, as they normally don't get along, so this is something to keep in mind as often once single tailed goldfish get bigger they can become quite boisterous.
Single tailed goldfish are better suited for ponds as they grow quite big and need far more space than fancy goldfish.... hmmm how long have you had the fish for?

Glad to hear Dory is doing okay! If the fins are fine, I would simply suggest making sure the water quality in her/his tank is very good, it sounds like it might have been ammonia or nitrite bothering them. Do you have a water testing kit or a fish store that could test the water for you? I would suggest testing both tanks for ammonia, nitrite and nitrate.

Okay so 5 fish overall in a 290 litre tank and from what I understand they're all single tailed goldfish right?
Your tank is massively over stocked with these fish, which means water quality may fluctuate and could possibly have been the cause of the issues with Dory.

Also with regards for water test kits, if you can get a liquid one I would recommend getting one. They work out more economical as you can get more tests out of them than you can using strips, so it would save money in the long run
I've had my liquid tests for over a year and still have tests left

I'm really not sure what to suggest for the long run, you have a few options, you can re-home some of the bigger fish in Spring, to someone who has a pond, generally a size of 5 inches is best to move a fish from a tank to a pond. So Waffles, Flounder and possibly Dory (depending on her size) could be re-homed. Sadie and Sally would be okay again, until they are a bit bigger.

Another option would be to consider having a pond yourself or buying a larger tank, but in all honesty a pond would be the cheaper option for you as large tanks carry a hefty price tag.

You're tank is ideal for fancy goldfish, but isn't big enough for the single tailed varieties permanently, not only because of the size they grow to! They can reach up to 30 cm's and need adequate space for exercise But also because the fish are very messy and in small spaces their waste can build up and cause fish in the tank to become un well (as you've seen with Dory).

Please read this for further information; (Link is not visible to guests. Please register to view.)

And also this; (Link is not visible to guests. Please register to view.)



[image]


This chart shows how big single tailed goldfish should be at 2 years

So your tank would only be suitable for one or two single tailed goldfish while their young and those fish would need upgrading, not 5 permanently I'm afraid.

Now I can appreciate this a lot of information to take on board, so please take your time to consider what you'd like to do, as it's clear you care a lot about your fish and you have taken good care of them

Myself, I can appreciate the situation you're in, I have a single tailed goldfish in a 100 litre tank, she is stunted from living in a smaller tank before, but I intend to upgrade her to a pond as soon as she reaches around 5 or 6 inches. Whether that pond home will be with me I'm not sure, but I might have to re-home her.

It's great that you saved some black moors, as I said once before your tank is a good one for fancy goldfish varieties  

I've had Lucky for over a year now, so I imagine she's just over a year old (at a guess).
I rescued her after a fair as someone had won her and another fish at a stall but hadn't wanted to keep them, so I took the fish home with me. I wrongly kept them in a 21 litre/5 gallon tank, but sadly we lost Star within a week and it was then that I started to learn about how to properly care for goldfish! Lucky spent another 5 months or so in the small tank, with my increasing knowledge I was able to take better care of her and cycle the tank properly by water testing and changing the water.

I upgraded her tank in January to a 3 foot, 90 litre/23 gallons tank, where she has lived ever since  
Because of her time in the smaller tank she is now stunted, meaning her growth is slowed significantly. If you look on the chart I posted before a goldfish aged a over a year should be around 5 or 6 inches. Lucky however is only 4 inches!

At the moment, I'm going to see how big she is next year in the Spring and if she is big enough, I have decided that I will re-home her then, because sadly I move around a lot and can't have a pond for her myself. I have considered every alternative option to a pond that I can think of, but I don't know if I'll be in suitable accommodation that could house such large alternatives!