well im trying yo cut some budget corners and have a GSP 29g tank at sg.016, im going to be gone for 5 weeks and im trying to explain water changes in a brachish tank the person taking care of my tanks. my thought was to go full marine and get the skimmer live sand ect. but live rock is spendy, and from what i have read its the sustrate that does the most. so my main question is could u buy some live culters to make my oregon lava rock come alive(im not going to have any inverts any way cause thay would be an expencive lunch for my puffer) i have 3 chunks in there now for my nitrogen cycle, but has any one done this in a full SG?