Help!!!! first bubbler grow

So i'm doing my first hydro grow only done soil before and as i have lifted one of my 6inch net pots out of the bucket i can see the bottom layers of my clay pebbles are covered in this white sludge and i can't think what it is, i have no pictures at the moment but i can easily describe it it is milk white and looks like thick snot clumped on the pebbles. Any ideas what it could be without the pics plant is perfectly healthy for the moment and i'm not using a recirculating system so not too worried just want to know what the f#*k is going on, bacterial growth of some kind???

you my friend have the SLIME!!! Caused by high water temps and light leaks through to the water. Flush you system, Clean ALLL the pebbles, and check you temps of your water - if its warm to the hand then its to hot, and make sure you have no light leaks - from the top of you bucket into the water. you may have to also buy some Aquashield or Physian 20 (sp) to help. This should help. Invest in a PH meter also your gna need one of those.

Thanks for that, the res temps were too hot checking them while trying to get them back down to the right temp was when i noticed the slime didn't know it was down to high temps though i was just readjusting temps so i didn't cook the roots so i learned something new today(never had that problem in soil). I will flush the pot when i get home and i did have a ph metre 2 days ago but it was cheap shit piece of crap that cost me £28 new and broke not soon after first using it... it was a tec-hu te10 if anyone wants to know what to avoid costs about £18 now and at that price for a reason. Anyway thanks for the info can you tell me is this slime harmfull to the plant because i just germinated some himalaya gold and can just start over if i need to as plant is not that far along.