Bloating Tadpoles, Please Help!!

[Raging Crocodile]

I have about 50 red legged frog tadpoles in a 30 gallon tank, i got them as eggs a few weeks ago and they have been fine, but now, about half of them are starting to get very bloated and see through. I noticed that a lot of them at the pond i get them from are doing it too. an someone tell me whats causing this?

[Raging Crocodile]

The tadpoles are also having trouble swimming and some are just upside down all the time

[herpdoc]

Try cleaning making sure they have clean water, that the tank is not overstocked. It may also be ranavirus. Btw, aren't these guys protected??

[Raging Crocodile]

I cleaned their tank and put in a few moss balls and a small filter, i also released about half of them, hopefully that will keep their tank clean. Another thing i noticed is that many of them have developed these strange white spots on their tail, as well as very small blood spots in the bloated area, but its different from what you would see if they had ranavirus, the bloated ones seem to just be full of water and are completely transparent in the bloated area. Also i know in California red legged frogs are protected, but i live in Seattle and they are absolutely everywhere here.