I am pretty sure ammonia is bad for all animals in the tank. That's why when people do fishless cycling there is no living animals in the tank. And at 7ppm that's kinda a lot. Most people cycle their tanks at 1-2ppm. With that high ammonia you can hinder the growth of your beneficial bacteria.
They probs can't survive that much ammonia but I'm not great with inverts. I would let the tank cycle and do some water changes before adding anything.
I think ammonia is toxic to all living things, though how much tolerance they have might differ. With it that high, I would probably wait until it started to come down before introducing anything but plants.
Also, there are differing opinions on this, but that might be too high for your tank to cycle properly? Most of the advice I've seen recommends 1-4ppm. There are people who've pulled off fast cycles with it much higher, though, so your mileage may vary.
