# does changing substrate break cycle?



## BBradbury (Nov 8, 2010)

*Changing Substrate*



Phish said:


> I am trading out my flourite red with some flourite black sand (why I ever got red substrate for RCS is beyond me)
> 
> My question is, if I use the same tank, filters, plants, etc., but 100% swap out the substrate will the tank still be cycled? It was always my understanding the beneficial bacteria lives on the glass and filters quite a bit.
> 
> Also, the flourite sand does not do any kind of ammonia spike or anything does it?


Hello P...

Good bacteria lives on anything inside the tank that has a surface. So, if you remove all the substrate, you'll remove a large percentage of the good bacteria. If your tank isn't too heavily stocked, you should be fine. The good bacteria will reproduce quickly.

However, if you have a lot of fish in the tank, you could cause what is referred to as "new tank syndrom". This happens when there's more waste in the tank than you have bacteria to remove it.

Just a couple of thoughts.

B


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## Dmckmc (Jan 22, 2012)

I replaced my substrate twice (different tanks.) The first time, I killed most all of my fish. The second time, no problem.

If you keep the same water and filter media, you should be okay. I believe my fish died due to a release of high levels of nitrite from the decaying material trapped in substate. The substrate was about 6 inches deep (marine tank with a deep sand bed) and very compact. 

The second time, the substrate was only 3 inches in a fw tank and was not compact. I would stir the media a little at a time a few weeks before the swap, just to slowly release any gas before doing the swap.

Now, I'm certainly not an expert - I'm just sharing what happened to me and why I think it happened.


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## Phish (Apr 29, 2009)

I should have said this is just for RCS. Which are prolly more sensitive than fish? 

I'll prolly just fully cycle it in a diff tank and then transfer the shrimp out. Doesn't seem worth the risk i guess


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## shrimpedout (Sep 14, 2012)

I completly rescaped my shrimp tank once (didn't remove substrate) but it still really stressed them out. 

I'd actually really like to do it again but I'm afraid I might kill the rest off.

---
Get shrimped out!


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## Diana (Jan 14, 2010)

Very roughly about half the bacteria live in the filter on all the media, about 25% live in the substrate, but only in the upper layer where the oxygen level is really high. The remaining bacteria live on all the other surfaces in the tank such as rocks, driftwood and ceramic merpeople. 

When you remove a substrate you are doing many things, any of which can stress the livestock:

There may be minor levels of toxins in the lower levels that are released when the substrate is disturbed. 
You are removing roughly a quarter of the nitrifying bacteria which can cause a mini cycle. A few days of a blip in ammonia and nitrite. 
The mulm in the substrate gets into the water and can cause problems in the gills. 

I would do this:
A week or more before:
Deep vacuum about half the tank and clean the filter. 
A few days before:
Deep vacuum the other half of the tank and clean the filter. 

The day of the swap:
Prepare 100% or more new water.
Remove the livestock. (Covered bucket)
Do the swap, set up the new hills and valleys, rocks and driftwood. 
Plant, misting often. 
Refill by pouring the new water in over a plate or plastic bag, allowing it to seep into the substrate slowly over the edges of the plate. 
That method of refill ought to minimize clouding, but if it looks too cloudy as you start filling do a water change. This is why I suggested you get ready with more than 100% new water. 
Add the livestock back to the tank. 

Additional tips to conserve the nitrifying bacteria:
1) Skim the upper level of the substrate and save it in several (3-4) bags such as nylon stockings. When the new set up is ready, hang these where there is good water flow. Remove then one per week. 
2) Buy bottled bacteria that includes _Nitrospira_ species of bacteria. Do not waste money on any other.


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## Phish (Apr 29, 2009)

Thanks Diana, good advice. I have been doing what you suggested to prep. The sand arrived today so I am looking forward to digging in and making some changes 

I notice you do not mention rinising the sand before usage. Is that not neccesary if I do the bowl method patiently?


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