Tadpoles
 

Hi guys, just joined here, well been here before reading but thought it time to post.
Been a avid hydro guy for years now, all mostly flood and drain, works good for me.
This season I,ve come across a possible problem not encountered in all my years growing. One of my tanks has been populated by tadpoles. Hundreds of the little buggers in one of my 60 litre tanks.

Question here is,
1) will they do damage to my cucumbers,
2) what do they do to my nutrients.

They are very very small at the moment.
So, WHAT do I do.
Cheers.