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Discussion Starter · #1 ·
I set up my planted 20 long just a little bit over 3 weeks ago. I am currently cycling, and waiting patiently for it to finish up so that I can get some fish in there!



But, when buying some BDBS I accidently bought the fine type. I recently bought a bag of Fluval Stratum and would like to swap out the substrate. My plan was to siphon out all the sand, drain the tank into buckets (I have about 15 gallons worth of bucket storage) and run my filter in a bucket until I can finish putting in my plants and substrate.


Does this sound like it will work? I am worried about disrupting the cycle. Any suggestions or does my plan seem sound?
 

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Discussion Starter · #4 ·
Would it be better to wait until it is done cycling? Currently I am at the point when ammonia gets zapped really quickly by bacteria and the nitrites are high, too high to accurately monitor any shifts with the API kit.
 

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There is more of a chance from my experience to ruin a cycle in a tank by taking out the substrate vs taking out the filter. Ultimately more of the BB will be in the tank not the filter.

What you can do is vacuum out a portion of the existing substrate at a time, lets say 1/8 or so and replace with the new substrate. Wait a few days and do another portion, until it's completed.
 

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I would do as Asteroid said . I did my 75 from gravel to BDBS . I made a couple of dividers from acrylic and did about a quarter of the tank at a time over the course of a few days and didn't lose the cycle at all . The dividers kept the two subs from mixing .
 
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Is this the case even with a bag of bio filter media in the filter? I have always read that the filter has much more BB than the substrate.
It's been a hotly debated topic here. In most cases if you have a normal size canister/HOB and you have a normal size tank 2 to 4 feet or so, from my experience there is much more BB in the tank, especially if it's a planted tank since the BB is on all surfaces.

There is nothing magical going on in the filter that isn't also taken place in the tank and there is much more surface area in the tank. I've killed all my BB in my filter over the years and the tank did not cycle, but remove all the substrate and it will in most cases.

If you have a small nano tank that isn't well planted and an extra large filter the above might not hold true.
 

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To add no one seems to have a definitive answer on how quickly the BB repopulates to rehome a given item (substrate, filter part, new plants....). The substrate is a big area so getting rid of a big area like asteroid said will have a impact. That being said you dont have fish in there, you have a filter to essentially seed with, and whatever plants and objects you take out and put back in as long as they stay wet should maintain the BB you currently have.

IMHO I would just do it now, get it to like you want and deal with maybe having a little extra time doing your cycle. Thats just me however, sure there are plenty that will disagree with my thoughts on it.
 
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