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Fish Fanatic
Sep 9, 2014
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Hi Guys,

I have been keeping Discus, (9 of them), in my 450L planted tank now for just over 6 months and it has been going great. However, in order to achieve the look I envisaged for the tank I have my heart set on completely swapping my current gravel substrate for "Amazonia". How should I go about executing this: I have sufficient vessels to accommodate 50% of my water but would be willing to buy another couple of bins to accommodate all of it if necessary.

My first plan is as follows: remove fish, turn off filter, remove 50% of water, remove old substrate, dump in new substrate, give it time to settle, turn filter back on then re-introduce fish.

Plan 2: Alternatively, I could remove all the water and old substrate then put new substrate in the dry tank then drip-feed the water back in to prevent loads of substrate becoming suspended in the water column then given some time with the filter on re-introduce fish.

My primary concern is about the safety of the fish: Will they be alright in a bucket of tank water, (with a heater and lighting), for the duration of this process? Also, I won't have to give my filter media time to re-adapt after the swap because it was already adapted to an extremely high load?

What do you guys think-any help much appreciated.

Thanks in advance.

Best wishes,



Fish Addict
Apr 17, 2017
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they will but attach the filter to the bucket, both plans seem fine. I would go to lowes and buy a rubbermade garbage can and put them in there during this exchange because it takes almost 3 hours to "settle"


Staff member
Global Moderator ⚒️
Nov 28, 2006
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Teesside, UK
I agree with Dutch, put the filter on the bucket or whatever you use. But don't put the light on it. Keep the fish in the dark, and cover the bucket; an old towel is OK for doing this. You need to keep the fish calm, and covered and unlit goes a long way to help.


Supporting Member
Tank of the Month!
Feb 25, 2009
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I have changed the substrate in my tanks several times all told, most recently moving from fine gravel to play sand. I would strongly recommend a temporary tank, not buckets, so the fish can be left for several days. When I changed over my largest tanks, a 5-foot 115g and 4-foot 90g, it was not done in one day; I did not want to be rushed [I have used a bucket method but never again]. The fish will be less stressed in a tank, with the filter and heater and a cover, and some decor to provide shelter, like floating plants, etc.

The substrate is where the majority of bacteria in an aquarium live, so changing it is a "big deal." Keep the filter running without cleaning (a rinse in tank water won't hurt if you think it needs it), and keep any decor like wood wet in tank water. This will preserve some bacteria. The water itself is not beneficial, with one exception. I always siphon the tank water into the temporary tank and net the fish over. When the tank rescape is ready, fill it with fresh water and use a good conditioner. Do a 50% water change in the temporary tank (using fresh tap water conditioned). With particularly sensitive fish, I would then half fill a bucket with the temp tank water, net in some fish, then slowly fill with water from the main tank to mix them. Net the fish into the tank.


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