Allotments 4 All

I have an old bath tub at the allotment which has been sunk into the ground.  The frogs spawn in it but I dont think they have started yet. 

It is full of rubbish and sludge ect.  Should I tip the lot and refill with rain water whist checking the sludge for any life that can go back in.

Any suggestions on getting it a little cleaner or should I just stick gloved hands in or a net and remove any large debri?

thanks in anticipation

It might be 'easiest' to empty all water with bucket..maybe in waterbut?..then clear majority of the sludge off leaving bit on bottom for frogs/tadpoles to hide in and put the water back in..yes, same water.. ;)
As your tub is sunk, digging it out sounds harder job than bucket job..

Why didnt I think of that  :)..... keep all the good bacteria etc in there to support new life.

Thanks goodlife

Why do you want to clean it out? If it's healthy, and not stinking or anything, leave it as it seems to support a healthy wildlife population.