I am upgrading my 10 gallon and 20 gallon to a 100 gallon tank and want to make sure I do it right and cost effectively. I have lots of live plants in my 20g. I used smooth river rock with that ugly red flourite stuff. I am planning on using sand in the new tank. Do I need to have some plant substrate under the sand, if so which kind is cheapest? Can I get away with using supplemental tabs? I use flourish tabs and they really helped my plants. I am thinking of using pool filter sand because I can't seem to find any of that quartz around where I live or online to buy. If you know of a place please let me know.