I sold this small tank to my friend that live near me with a back wall of GSP that was completely fine we he came by and took it. I drain the tank water to a container and just leave the sand bed in the tank with the old filter media in the filter chamber. The sand got stired up during transportation but it was a thin layer sandbed (1-2cm/less than and inch). Tank is about 20liters/8gallon. He brought home and put back the water in with the new dry rock as layout. The gsp in firstday after sold still open but day later start to close and have these brown thing on their heads. Any ideas what they got and anyway to save the gsp? Thanks!


