20 Gallon Tank Very lethargic goldfish

Tank
What is the water volume of the tank? 90 L
How long has the tank been running? 6 months
Does it have a filter? Yes
Does it have a heater? Yes
What is the water temperature? 21c
What is the entire stocking of this tank? 1 goldfish (approx 3 years old), 4 nerite snails, 4 amano shrimp

Maintenance
How often do you change the water? Weekly
How much of the water do you change? 20%
What do you use to treat your water? Seachem Prime
Do you vacuum the substrate or just the water? Substrate

*Parameters - Very Important
Did you cycle your tank before adding fish? No
What do you use to test the water? API Freshwater Master Test Kit
What are your parameters?
Ammonia: 0.25
Nitrite: 0
Nitrate: 3.0
pH: 7.0

Feeding
How often do you feed your fish? Daily
How much do you feed your fish? Deshelled pea or a couple pinches of flakes
What brand of food do you feed your fish? Tetra
Do you feed frozen or freeze-dried foods? No

Illness & Symptoms
How long have you had this fish? 3 years
How long ago did you first notice these symptoms? 3 weeks ago
In a few words, can you explain the symptoms? Initially noticed lethargic, sitting upright but still on the floor of the tank for long periods. Moves around as normal when being fed. A week later, noticed a large lump on upper side, which turned into a reddened wound. I dosed Pimafix and Melafix, the lump went down and the area around it has turned black, as has some other small patches. Still lethargic, doing really long poops.

Have you started any treatment for the illness? 7 days dose of Pimafix and Melafix. Also used Interpet anti internal bacteria as I thought this may have helped.

Was your fish physically ill or injured upon purchase? No
How has its behavior and appearance changed, if at all? Normally very active, lays still nearly all day now. Some small black patches on body

Explain your emergency situation in detail. (Please give a clear explanation of what is going on, include details from the beginning of the illness leading up to now)
I've seen little worms occasionally float around in the tank, which I think are detritus and not harmful to the fish. But I'm worried they may not be something else. Been almost a month now and my goldfish barely moves all day
Any help would be hugely appreciated! Thanks
Some photos

 

Any indication of ammonia in a tank which should (after an adequate period of time) have a natural cycle should be a cause for worry. Larger water changes could help. As for the black spots... those can come from a huge variety of things ranging from very concerning to not concerning at all. The hard part is determining which it is. The two most concerning are parasites and ammonia poisoning... which either could be possible based on the fishes lethargy.

It’s also difficult to treat the fish with medications when you are unsure of the cause. This can actually be detrimental as any medications normally increase the stress on your little friend.

Sitting on the floor of the tank points to have a swim bladder issue which affects the natural buoyancy of the fish. These are common in goldfish and can be prevented with great water conditions and a proper feeding routine.

Lumps are also common in goldfish and aren’t lethal but can be quite unsightly. They can be prevented with pristine water conditions.

I’m going to go ahead and say most of these things point to poor water quality. Let’s go ahead and try some large water changes; 40-50% every two days for a week... and we can revisit the issue after the water is hopefully clean and healthy once more. A small dose of Aquarium salt won’t hurt either as it helps cycle some of the nasty stuff out of the fishes body.

 

Thanks for this Smangsty, much appreciated! I'll hold off on the medication, carry out the big water changes starting today and reassess in a week or so

 

Thanks for this Smangsty, much appreciated! I'll hold off on the medication, carry out the big water changes starting today and reassess in a week or so

Great work!! I look forward to hearing about their improvement and I’ll be here if you have further questions.

 

So i did a 50% change this afternoon and tonight I've spotted a couple of tiny white bugs swimming around. Here's one on the glass. Never seen them before and don't have a clue what this could be...

 

So i did a 50% change this afternoon and tonight I've spotted a couple of tiny white bugs swimming around. Here's one on the glass. Never seen them before and don't have a clue what this could be...

Oh that’s pretty interesting! It looks like a Cyclops which is a type of copepod. Cyclops live in freshwater, such as ponds and lakes. They prefer areas of still water with a lot of algae. It’s likely you could have picked one up with a rock or plant addition to your tank habitat. Many aquarists consider them valuable as a fish food and even sell them. I would not be overly concerned with them for most aquariums as long as good aquarium cleaning methods, such as vacuuming are practiced; in fact as noted earlier they actually make a nutritious fish food.

EDIT: Looks like the forum removed my picture example due to copyright! If you google “Copepod Cyclops” it should bring up some great reference images to compare with.

 

We lost our little fish today unfortunately. Scale blackening kept getting worse throughout the week. No appetite this morning, inability to get off the bottom of the tank and rapid breathing. Tried setting up a hospital tank but it was too late sadly. I must have left it too late doing the major water changes, really gutted
Really interesting about the cyclops'. I had no idea they existed! Still seen a few of them in the tank and the shrimp and snails all seem fine.
Thanks for your advice for my question Smangsty. Not quite the outcome we were hoping for but I really appreciate you taking the time to help out