something growing and its alive

Question
i had put in a garden pond and i love it.  i have koi and tadpoles in it.  i found a few snails in it how did they get there? were they on the plants i purchased?  also i have these thing growing in it.  they are small have a long body and 6 or so legs.  i want to know if they are mosquitos or if they can do damage.  they live in the muck at the bottom of the pond.  any advice would be appricated. thank you
lee ann

Answer
LeeAnn, Looks like you did everything right. The snails probably came on the plants, snails purify water. It is difficult to say exactly the creature you are talking  about
if this is an insect type creature likely some kind of water beetle. No need to worry. Wont harm anything. That is when you know everything is OK you will find some strange frogs will adopt your pond during the course of the year, just enjoy your pond
               KEEP PONDING
                    Leigh