Thats the fun of it for me...my tanks are all in constant flux, both SW and FW. Aside from having an established cycle they are never in a period of stasis, I'm always changing plants or rockpiles or driftwood configurations, looking out for new plants or corals. The largest cost is the up-front purchase of the system. Now, if you start off FOWLR and then decide to go reef, yes a few powerheads and some nice T5 lighting could make another big dent in your pocket. But, once you get it set up, you can do a lot through trades. I started off purchasing maybe 2-3 different types of plants and now have maybe 10-15 through trading with people. With corals, find some local reefers and trade frags, many will even sell you frags pretty cheap. Thats the only way I'm able to afford constantly getting new stuff...If I were always paying LFS prices I'd live in a cardboard box.
