Changing Subtrate

[Ulrum]

So when I first got my tank, I filled it with red and black colored gravel and plastic decorations. As I've been slowly moving away from that, I've hit a wall because I don't know the right way to replace the gravel without a lot of the surface area for beneficial bacteria being destroyed. Any thoughts?

[anewbie]

Most of the bacteria is in the filter but you can add a sponge filter if it makes you feel more comfortable (to be sure it would need to be in the tank several weeks to have any effect). Anyway i've replaced substrate a few times - what I do is as follows (the specific detail depends on the size of the tank  - the largest i've done is a 40B):

put aquarium water into a 5 gallon pail - put fishes in pail - put water in another 5 gallon pail - put plants in second pail - finish draining tank - remove all substrate  - put in new substrate  - fill tank with treated water - make sure temp is normal temp - put fish plants back in tank - put fish back in tank - measure ammonia next few days to make sure cycle is not broken. 

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I used a pet scoop to remove the old substrate (sort of like what you might use for large bag of dog food).

Edited April 23, 2021 by anewbie

[Streetwise]

There are many substrate strategies. If you restart a tank with a new approach, I recommend saving all the leftovers in buckets or tanks. You might have some really cool inhabitants.

[Ulrum]

So what I've read on the subject varies a lot, from saying that the filter carries the majority of the beneficial bacteria, to the idea that the substrate carries the most because it has the highest surface area, to the idea that every surface matters and can cause a problem.

[Streetwise]

Every bit of surface area can host beneficial bacteria.

[Hobbit]

As long as you preserve some of the bacteria (for example, in the filter and on the plants), you’ll have enough bacteria to start your cycle again fairly quickly. Just watch your parameters carefully for a few weeks after the change, and do a water change if you see ammonia or nitrate.

I’ve wondered about changing the substrate in my 55 gallon but I can’t take out all of the hard scape, and I don’t think I could catch all the fish. I think I would have to siphon the gravel out.

[ChemBob]

Feed very lightly after a substrate change. Slowly increasing feeding back to normal after the change, over a few weeks. This will help minimize the impact of losing the bacteria in the substrate. You can also get mesh filter bags or equivalent, and put a bunch of the gravel in it. Place this back in the aquariums after the initial change and remove some percentage of the gravel every couple of days. This will help preserve some of the bacteria as you make your transition and help seed the new substrate. 

[Anita]

1 hour ago, ChemBob said:

Feed very lightly after a substrate change. Slowly increasing feeding back to normal after the change, over a few weeks. This will help minimize the impact of losing the bacteria in the substrate. You can also get mesh filter bags or equivalent, and put a bunch of the gravel in it. Place this back in the aquariums after the initial change and remove some percentage of the gravel every couple of days. This will help preserve some of the bacteria as you make your transition and help seed the new substrate. 

And keep the substrate, loose or in bags, immersed in water. Many of the bacteria will die if they dry up.