Is it possible to change substrate in an established tank? - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 4 Old 06-20-2014, 08:18 PM Thread Starter
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Is it possible to change substrate in an established tank?

The tank in question has been going since last September and I've had multiple fish in it since then. I got new fish after my original 2 died and left one descendant behind, and I was given one from one of the clubs in my school. Now I have an idea for a new theme going off of all of the inhabitants' names. It's a 10g with 4 fish and 3 shrimp. It currently has gravel as substrate and it always gets dirty and is hard to clean even with a gravel vac. I would like to switch to sand and possibly even change the decorations.
I know that the gravel holds bacteria in it, so my idea was to remove some and replace that with sand, repeating the process until eventually all of the gravel is gone. And if I don't take all the decorations out, I'd just move them around.
Can I do this and is there a special way to do it?

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post #2 of 4 Old 06-24-2014, 10:28 AM
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Nothing really special about it. It's just a pain.
Your method will work fine, but I think if your gravel gets that dirty very often, are likely overfeeding? Sand won't really help with that issue and sand gets "dirty" too. Cleaning sand can be a tad tricky since it's easy to siphon sand out with the waste.

Depending on the fish load and filter, you might do just as well (especially if the gravel is dirty) to remove it all at once, do a massive water change, and add the new stuff. Remember though, as you mentioned, the "dirty" gravel does have a lot of biological capacity.

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post #3 of 4 Old 06-24-2014, 10:44 AM
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Is it possible to change substrate in an established tank?

I've completely swapped substrates in one shot many times. There is a loss of bacteria but my filtration systems were large enough to accommodate the population explosion of the filter colonies, so the impact on the cycle was minimal. I dosed with prime and fasted the fish for a few days and all was well.

If the filtration system is not capable of handling the entire bioload of the tank, meaning it is dependent on the substrate colony, then I don't think it will be as smooth of a transition.

If you want to play it safe you can get a couple of media bags and fill them with gravel. Make the switch and leave the bags of gravel on top of the sand. Then after some time you can remove one bag and then later the other.

With regards to vacuuming - don't be afraid of sucking out some sand. It's just sand. You can always add more when it starts to look a little low - it's very easy to add more sand to a tank.
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post #4 of 4 Old 06-28-2014, 10:25 AM
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I did what jaysee advised and I've done it several times without any issues. Much of the bacteria does live on the decorations as well, so if you've got a high bioload you may want to keep the decorations we and change those out after around a week. But, most of it is in the filter and substrate so you should be fine either way.

I kept some of my old gravel in a stocking for a couple weeks just to be safe.. Just keep an eye on things.

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