The skin peeling sounds like some sort of infection, so I would treat it with Esha 2000.

It's not overstocked, but the advice is poor, as Neons and Otocinclus need the water to be cooler than a Betta prefers. Neons can also be fin-nippers, so they may nip at the Betta's fins, and Bettas are potentially quite aggressive and may bully the other fish. Usually, we'd advise that a Betta be kept alone in a 40-litre tank.

Click on the forum name you want to post in (e.g., Tropical - Help and Advice). At the top of the page is a green button marked "New Topic." Click that and make your post.

Looking at their web page, yes, if you want the tank to look less red/blue.
https://ciano.pt/en/produto/sistema-led-cle120plants/

No they can't be used together. Give the Flubendazole 48 hours to work then do a 50% water change and add carbon to your filter for 24 hours to remove the rest of it before treating with Esha 2000. Don't forget to remove the carbon before staring the Esha 2000.

As per my post above, Esha 2000 - available in many shops and online at Amazon.

Rainbowfish are highly susceptible to mycobacterium infection (fish TB). While this does sound like it, it could just be a bacterial infection which will clear up with Esha 2000. This is safe for all fish. If it doesn't clear up with treatment then mycobacteriosis is more likely but can only be confirmed with a skin scrape tested by a vet. Unfortunately, there is no cure for this and the usual recommendation Is to euthanise the fish and completely strip and disinfect the tank and its contents before starting again.

They are all much the same, and the safest thing to do is a full fishless cycle with an ammonia source. See this article: https://www.fishkeeping.co.uk/articles ... hless-cycling-article.htm

Hi

As this is a new tank, did you do a full fishless cycle with ammonia before adding fish? If not, then you are cycling fish in and the minnows most likely died of ammonia poisoning. The rest of the fish will be at risk until the cycle is established so you should follow the advice on this link: https://www.fishkeeping.co.uk/articles ... ammonia-nitrite-spike.htm

Hi

I believe these are breeding tubercles that appear on sexually mature males from time to time when they are ready to breed. They appear particularly on the leading rays of the pectoral fins and can also occur on the gill covers and on the leading rays of the pelvic fins. They will go away after a while but will probably recur, and are nothing to worry about.