Strange growth

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I was feeding my discus today and noticed a small growth at the tip of his dorsal fins. At first I thought it might be a pond snail on the end of the tip as it looks very similar. I have had a pond snail outbreak (small) lately. It is not effecting his appetite etc and he seems otherwise healthy. I have noticed it is white and almost like a 'wart' except small.

Any ideas?.
Thanks