Hello, hope someone can help my goldfish, s/he's in a pretty bad way.....

We bought 2 goldfish about 6 months ago, we didn't really know much about keeping fish so we bought a classic goldfish bowl (approx 5 gal) and did a 100% water change every 2 weeks, as we did not have a filter. Recently it has been very hot here in the UK and during this time the water became very mirky and green and was probably not changed as quickly as it should have been. Once the water was changed the smaller of the two fish started to get black marks on the tips of its fins. I looked on the internet and read that the marks could have been due to amonia burns, this is when I became really concerned and started to research into looking after goldfish. Since then I have purchased a 'proper' aquarium with a filter, a gravel cleaner and doing regular 25% water changes (Water treated with 'Nutrafin Cycle' and 'King British - Safe Guard' and left for 24 hours before using) The fish were introduced to the new aquarium as instructed however a few days later the small fish had white cotton like fungus growing on its side, I looked on Ebay and bought some 'Fish Saver' to clear the fungus. At this point the fish was lifeless and just sitting on the bottom. A few days later the fungus had cleared up and the fish became lively again, however the tail started to rot, the fish saver was also for the treatment of fin rot so I continued to use it...4 days later and my goldfish no longer has a tail, it does however have some 'bones' left. I have now removed the fish from the main tank and created a hospital tank, again with the cycle solution and the safe guard and left fo for 24 hours. I also bought some recommended medication called 'Myxazin'. Am I doing the right thing? Is there anything else I can do?, will the tail grow back, if not will the fish suffer without a tail?
It might be worth mentioning that the other goldfish in the tank seems to bully the little one into a corner would this cause a problem?
The little fish also has a blister bubble on one of his/her guils, and a few black marks one around the eye and around/in the 'nostrils'

Any help will be greatly appreciated, I have photos if required..

Many thanks
Drew

Test Results
- Tank water
PH - 7.5
KH - 7
GH - 10
NO2 - 0
NO3 - 20

- Tap water
PH - 7.5
KH - 17
GH - 10
NO2 - 0
NO3 - 20

Tank Size - 4.5 Gal
Filter - Elite Stingray 5
Water Change - 25% every 2 days while ill - otherwise weekly
2 Fish in tank one approx 3 inches other approx 2.25
Food - Nutrafin Max

Welcome to the site, sorry to hear you started out with problems.
As I am sure you know, while the tank you have is better than a bowl it is still not enough to ensure a healthy environment for the fish.
GF require 10-20 gals each. This is to help keep the water quality at peak quality.
With such a tiny tank you may never end up with healthy fish, sorry just the truth.
In the meantime keep the water in top condition by doing water changes every couple days.
I notice that you don't have a ammonia reading, do you have one?

Next, depending on how long it has been since they were in the bowl you still could be seeing repercusions from that.
It takes fish a very long time to heal once the water quality goes bad, and that is in optimal conditions.........so it may be longer (if at all) with their tiny tank.

What I would recommend is one a bigger tank, at least 20-30 gals. Next I would stop all meds, this can do more harm than good in most cases. Especially where water problems were the cause.
Perfect water can heal more than any med out there.

Good luck, keep us posted.

Thanks for your reply, unfortunatly the little fella gave up the fight last night and died. Looking at him today today he was in a really bad way, as I mentioned about the tail, it looks like the rot had taken the surface off the scales half way down his body. Last night I also noticed a white stringy substance near his eye. Thought is was just 'debris' but today his eye had a hole in it and was very blood shot. Thought he was gonna pull through too. Thanks again for your reply,it's a shame it took all this for me to realise how to look after fish!! Think i'm gonna look out for a bigger tank!!

I am sorry to hear he didn't make it.