White mold in floating in the filter area

Question
I have 1 year+ old fish tank (30 gallons). 4 Gourami  (1 Blue, 1 Opaline, 1 Dwarf, 1 Yelow), 5 neon tetras, 6 koi sword tail and recently born fry (maybe ~10). Initially I had just one koi sword tail and when I bought her, she was pregnant, now the population of koi is growing.
Recently I noticed in the filter area there is some white stuff (looking like a mold). It is floating only in that area and nowhere else. I changed the filter, cleaned the are with the wet towel and this white stuff (mold or fungus) is still there. It does not seem to effect fish - they look active and happy but I still worry. It has been there for a month.  How do I deal with it or should I just ignore it if it is not harmful to the fish.

Answer
Hi Ija,

It doesn't seem like much of a problem. It's mostly some sort of organism that's growing there. Since it does not seem to be affecting the fish at all, I wouldn't worry about it. You will notice if there's any major fish problem/disease anyways. You mentioned that it was "floating only in that area". If it's floating, you can just net it out, if it's unsightly, or bothering you. Other than that, I see no reason why you need to try and eradicate it.

In case you are not doing so, change at least 10-30% of the water per week to maintain water quality. The filter media should be changed every month.

Good Luck, and Happy Fishkeeping!