My mature 126 litre tank is pretty bare at the moment with only a couple of java ferns and not many fish so it seems like a good time to start over with new substrate and new planting. I currently have a mixed natural colour gravel in there which has been there for years and I want to change it for a black substrate. The inhabitants are 1 guorami, 4 chain loach, 1 rummy nose tetra. 2 wood shrimp, 1 armano shrimp and loads of dwarf blue shrimp- I'll be moving them into a spare tank whlie I do the changeover. I don't want to spend a fortune so rather than going for expensive growing substrate I'll probably go for something inert with root tabs, does anyone have any suggestions? I would like to add some corys at some point so nothing sharp. Also I don't want to kill my fish or have to deal with a cycle, will they be ok if i save most of the water and keep the filter running in sparetank while I'm changing things?