How To Change The Substrate Of A Tank Safely

  1. phenris

    phenris Valued Member Member

    Currently I have obnoxiously colored gravel in my 7gal that I want to switch to sand. I set the tank up a long time ago and have never done a complete gravel change, since I'm guessing that could impact the cycling. So I've just always done syphoning.

    Now, I hate the look of the colored gravel, my fish probably hates the colored gravel, and we both want it changed lol. How can I do this safely without affecting my cycle or doing a 100% water change if that's possible?
     
  2. endlercollector

    endlercollector Fishlore VIP Member

    I've done this many times though never on such a big tank. The key is to organize well, so that you can do it quickly. You'll need multiple buckets, and several 10 or 20 gallon tanks would help a lot. I used 2 20 longs and a couple of 10's when I redid a 29 gallon recently without buckets.

    First things first, rinse that sound a lot until it's where you want it. Put your filter on a temporary tank (or square bucket if you have one), fill it with water from the tank, and you can just keep the media damp, or you could even run it (assuming you have HOB--I couldn't find what you have). You can put some fish in there, plants, etc. You can spread out animals and plants in various temporary tanks or buckets. Just make sure that everything is covered in case of jumpers, and make sure the heat is even. You may need to use lower wattage heaters if it's not warm enough in your place.

    I would siphon most of the water into the various containers but then start dumping the water that's at the bottom where the gravel and sludge are. I have in the past just hosed old gravel into the garden, but now that we're in a condo association, I get it all into buckets, etc. I rinse it out well and then give it away through Freecycle. There's always someone who appreciates random gravel.

    I would then actually put down an inch of organic potting soil. Why not? You've come this far. Just spread it around evenly, and if you have plants to root, stick them in now, making sure they're where you want them in the long run. Then layer on your sand, and put lots of dinner plates on top. Use airline hoses and hold them in place with nets or other random items to refill the water gently. If you organize well, this should only take a few hours ;)
     
  3. sleow

    sleow Valued Member Member

    I was able to change from gravel to sand in my 36g all during one big water change. I took about 50% of the water out of my tank, then removed all of stuff in the tank, besides the fish. The fish weren't too happy during the part of the process but they'll be fine. Once it's just fish, I carefully took out the gravel one scoop at a time. Once the gravel is gone, I put the sand in the same way, one scoop at a time. I used an old plastic cup that one of my bettas came in and sunk the whole cup to the bottom of the tank before dumping out the sand. This helped keep the water clear since the sand was already settled. Make sure to rinse any sand you put in really well. I used pool filter sand and needed to rinse it for a good 10-15 minutes before the water ran clear. Once you spread the sand out the way you want, you can re-scape and plant any plants super easily into the sand. Some plants may need root tabs to thrive in sand though.

    I was able to do it this way in a couple hours with my fish still in the tank and without losing my cycle. My fish were much happier because of it! Good luck!