I might be blind bit any pics of it it may not be gha it may be bryopsis is it hair like or does it look like the pic I posted? If it looks like that it is bryopsis and can not be kill vja regular means as it has the ability to break down food itself also once gha gets long most snails won't touch it if the tank is still within 6 months of being setup then your most likly your the green part of the cycle and you just need to increase water changes and it'll go away another way to rid it in the dt is setting up an fuge or algie turf scrubber giving it a better home to grow in and itll slowly leave your dt in favor of growing in a more sutable area good luck and I hope you get it figured out one last thing durring an outbreak often your test will read 0 due the it using the nutrients up test you water right before the lights come on while the tank is still dark to get a more acurate read as it has not started using the nutrients built up overnight