White cotton like mould in tank

[clintonsavage]

Hello we have a siamese tropical tank and it has recently started to rapidly grow a white fungus or mould that looks like cottonwool in water. it can cover whole bottom and all corner edges slowly going upwards within a few days. We tried removing all water, replaced active carbon rings, all filters and pumps cleaned, scrubbed whole tank with hot water and brush. The tank then takes about 5-7 days for mould to return, but the mould always returns. Tank was cleaned today, so when mould grows back i will provide a photo. Any suggestions until then would be greatly appreciated.

 

[Fishfur]

Is this tank cycled ? Does it have fish in it ? Mould growth can be fueled by overfeeding, but it's not that common to have it take over like this.

What are the water parameters ? pH, Ammonia, nitrite, nitrate ? Temperature ?