They will grow back.
But dam you have nothing in your tank for bacteria build up.. I dont think your water is good.
You need media, or gravel or lots of decors, and a cycle for healthy water.
Do you have another tank that's been running for a while?
When was this tank set up and how old and where this water came from? If this tank is filled with new water from the faucet then there needs to be changes asap.
if that is the case, Take gravels and lots of decorations from a running tank and some of it's water and add new water to put this guy in..