fluffy gills usually happen when you introduce a sponge filter. Sponges add little air bubbles so I guess they oxygenate the water. Maybe you have more oxygen in the water than normal?
Fluffiness is thought to be a response to less oxygen, I believe. That is, more surface area on the gills is needed to take in the oxygen.
The warmer the water the less oxygen there is in it.
And still water will have less oxygen because your axies will be using it up; it is surface agitation that replenishes the oxygen more than bubbles. Unless you have enough plants to replace the oxygen.
Sponge filters give fluffier gills because the water does not circulate quickly to collect much oxygen from the surface.
Does any of that make sense?
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