What wrong with my tadpoles?

I have a tiny pond that I built because I've alwys had frogs in the garden and I hough they might like to have a swim, I also use to find frog spawn in puddles so I thought a pond would be a good idea.
In the spring it all went according to plan, the frogs moved in, not long after I had hundred of tadpoles. But now, in July, I still have tadpoles and no signs of frogs. Shouldn't they have turned by now? Is something happening preventing them from changing into frogs? :confused:

 

If the pond is at all overcrowded, apparently it's not uncommon for the tadpoles not to develop, and we did have a long cold spring. You could try decanting some to another pond, or try adding a few drops of iodine, which is needed for the tadpoles' development.

 

Years ago we had tadpoles in an aquarium in a classroom and they just grew and grew and showed no sign of turning into frogs. One the kids' dad was a biology teacher and his explanation was iodine deficiency in the water.

 

Liz, Dave,
Thank you very much for your reply, I don't think the pond is overcrowded but I will definitely try the iodine.
Is it something I can easily get hold of?
Regards, Fiwi

 

you should be able to get it at any chemist.

 

I've been meaning to get some iodin since reading this thread but my memory doesn't seem to last pat the front door!

 

How does it occur naturally? Is there a plant that produces it?

 

It occurs naturally in sea water and soil as iodide which is oxidised by sunlight to produce iodine. Seaweed is a good source.
Iodine is required in the human body (and in tadpoles too it seems) in order to keep the thyroid working.
I seem to recollect from either geography. history or biology lessons at school that iodine was at one time added to salt in order to prevent what was called Derbyshire neck (goitre).

 

Does anyone know how much iodine you would need to add to how much water to metamorhosise the frogs?. I would just leave them.