Advice for replacing substrate?

[captskinny]

Hi,

About 6 or 7 months ago I wanted to replace the course gravel in my tank with something finer that would not trap food and waste. After some research online, I settled on sandblasting "sand" as a replacement. The particular variety I got is coal slag: black, very lightweight, and doesn't pack together at all. The problem is that while fish waste settles on the top, my two 8 inch Plecos constantly stir up the substrate, mixing any waste into the substrate and making it impossible to vacuum up. I'm concerned about that waste building up and decomposing, so I've done some more research and decided to replace the coal slag with course pool filter sand. I know it will be heavier than the coal slag, and I'm hoping it will pack together better, resulting in much less mixing of waste into the substrate.

That said, what is the best way to go about replacing the substrate? When I replaced the course gravel (1/2 inch pebbles, really), I did about a 1/5 of the tank (12" x 48" footprint) each week, with the intent of giving the bacterial colonies on the gravel time to transfer onto the new substrate. This time, however, if I don't remove all of the existing substrate before putting the pool filter sand in, the two will become mixed within 15 minutes and I'll never get all of the sandblasting sand out. Is there any reason I can't just shop-vac all of the sandblasting sand from the aquarium (using a gravel vac attached to a regulating valve, not the shop-vac hose, of course)?

Thanks,
Capt. Skinny

[Sasquatch]

I agree that siphoning it is the best way to remove it, it's what I did recently with my substrate. It will probably cause a little setback in your cycle so I suggest keeping a close eye on ammonia/nitrite levels and having some ammonia sequestering substances on hand.

Also have plenty of treated water on hand. When I did the substrate change I had to replace the water several times and a lot of detritus had built up. Every time I added the water, more crud went back into the tank.

[captskinny]

Thanks, I appreciate the the advice Sasquatch.

[siymdapolio]

I agree that siphoning it is the best way to remove it, it's what I did recently with my substrate. It will probably cause a little setback in your cycle so I suggest keeping a close eye on ammonia/nitrite levels and having some ammonia sequestering substances on hand.

Also have plenty of treated water on hand. When I did the substrate change I had to replace the water several times and a lot of detritus had built up. Every time I added the water, more crud went back into the tank.

^^^^^^^^^^^^^^^^
Agree with sasquatch :thumb:
You can also you something like a small bucket(old butter jar) and scoop it out individually very slowly one by one... this is tedious but a lot better then trying to get it all out at once and make sure you siphon out half of the tanks water so you dont have to take all that dirty good substrate through the water. This is if you need to change it all at once

I agree dont take it all out at once because of beneficial bacteria hope this helps!

[Incredulous_Ed]

Ii would scoop most of it out, then siphon some out.

[helot13]

I would scoop a good portion of it out and put it into a pair of pantyhose. siphon the rest of the gravel out and replace it with your wanted gravel. Put the pantyhose-d gravel back in the tank as "seeder" gravel which will give you a jump-start with the bacteria. Then after a week or so, take the pantyhose gravel out.