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Re-scraping with fully cycled filter - when can I re-add fish?

James France

New Member
31 Mar 2019
Hi guys

So I want to re-scape my 120L which has been set up for 6 months now. It has a stock of 20 or so and is filtered by an Oase Biomaster Thermo 350.

If I reuse the same filter and media (just un-plug and re-plug within a few hours) and if I reuse some of the gravel and substrate, plus I plan to plant it heavily, when will it be safe to re-add the fish? Also if this is longer than straight away, does anyone have any bright ideas on how I can keep the fish healthy in the interim period?

Thanks a lot in advance



4 Jan 2019
Technically if you are using the same substrate and the same filter I would say immediately but keep a close eye on the nitrogen cycle. To be safe I would wait a week. Partially reuse the same water that you have in your tank currently. Store that somewhere.

In fact even in an un-cycled tank you can add fish if you know what you are doing and behave like a hawk and check water parameters daily and do the necessary to keep ammonia low.

Keith GH

28 Aug 2017
Melbourne Australia

So I want to re-scape my 120L which has been set up for 6 months now.

I assume (never assume) you will be removing all of the water if so keep your filter running in that water.
I bought a large plastic container for that purpose.

If you use this or a similar method I would say immediately.



24 Dec 2014
Easiest is to set up fish temporarily in a food safe bin of suitable size - I suggest 60litres or so as this should provide reasonable length/width/height and can usually be run on your filter (depending, most canister filters “expect” tank to be raised some minimum height above the filter, so can be a bit tricky to get going)

Just add a mix of tank and tap water as if doing a routine water change

There’s no need to store additional tank water for the rescaped tank

With filter running on the fish bin, there’s no hurry with rescaping the tank - a cover is recommended though as fish in a bin on the floor are often more “jumpy”

Get tank sorted
Add some water movement (if possible) overnight - I wait at least 24h just in case wood decides to float etc
Then add filter back - make sure it’s all going well
Then add fish

Then depending which soil etc, follow Tropica 90Day App
26 Feb 2013
As alto's suggestion.

When my tank broke down I kept 7 clown loaches in a plastic bin pretty much for about 2-3 months with the filters hooked, some of the emersed plants and daily water changes. They were no negative consequences. They didn't bother jumping out either although in much smaller than usual quarters.

And now, I even have plastic tanks running with fish for years, older plastic tank around 5 years and I have since setup two more, plus a big plastic pond, lol. Fish don't care if they're in glass, crystal or plastic...as long as the conditions are tank like, cycled and good water quality, filters hooked, etc...