Thanks for your suggestion Seds and Topfrog007, just one question though: after I get switch out the substrate, do I have to let the tank sit there for a couple days or can I just go ahead and add the fish right after I finish filling the tank?
1. Rinse the new substrate a few times depending on what it is...
2. When your ready for the transfer, Siphon out some water in a 5G bucket or Tupperware or something.
3. Move all fish/equipment this new container try to keep as much/all water from your current tank.
4. Take out the old substrate/put in the new substrate.
4A. Do any aqua scaping
5. Pour water in very slowly, so you don't make the water cloudy.
6. Transfer fish/equipment back into the tank.
7. Finish filling up the tank.
Since the water in your tank is already cycled you'll want to keep as much of it as you can. Also, your filter has built up bacteria which break down ammonia. Your fish should be fine
I hear ya on keeping costs down, that's a major concern for me too. I'm also very lazy so I prefer low tech/no c02/no water changes. The method I've successfully used in my 55G is here:
Since you mentioned keeping costs down, a very cost effective solution to expensive substrate is Mineralized Soil. Read about it here: