Silly gravel to sand question

qquake2k

AC Members
May 3, 2006
121
1
16
Northern California
I'm going to be switching from gravel to sand in my 46g bowfront. Would it be beneficial from a bacteria standpoint to leave a thin layer of the old gravel in the tank and cover it with the sand? Or should I remove all the gravel?
 
I just switched the gravel in my 55gal tank. I took out half and put in the new stuff, then two weeks later I switched over the rest of it. I didn't get any spikes, but this tank is part of a larger system so that lends some extra stability. I would say even if you do one half then a week later do the second, you should be fine, just keep an eye on ammonia for a day or two after the changes and do water changes if you get a mini-cycle, but it shouldn't be too bad.
 
I never leave old substrate, and have had no issues with spikes. If you have enough bio filtration media in your filters, I see no reason for any issues...it doesn't take long for the bacteria to repopulate.
 
I meant to mention before - my main reason for leaving it half and half for two weeks was to give the MTS a chance to populate the new substrate.
 
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