Nitrifying bacteria reproduction rates and removal of sand bed

[GroktheCube]

I'm currently in the process of removing my year old sandbed. I just did the first siphoning two days ago, and it very much reinforced my decision. Despite fairly frequent vacuuming, the stuff that came out looked and smelled dirtier than my skimmate usually does!

I'm wondering how quickly I can safely remove the sand without damaging my biological filter.

The only information I've found online suggests that nitrosomonas and nitrobacter are capable of dividing every 7-12 hours on average under "ideal' conditions. I doubt my conditions are perfectly ideal, but I was unable to find any information on how differing environmental parameters impact reproduction rate of these specific bacteria. These guys obviously reproduce very slowly compared to many other types of bacteria.

Would it be safe to assume that after 2-3 days, any lost bacteria needed to process NH3 would have regrown?

I intend to play things safe, but given I only removed about a fifth of my sand thus far, even if that contained a fifth of my ammonia processing capability, I'd only need a quarter of the remaining bacteria to double once over the course of 2-3 days to ensure the biofilter was back up to snuff, and that seems to be a rather conservative expectation.

 

[Nano sapiens]

Removal of an entire SB can be tricky. You are basically asking the various bacteria to repopulate and establish the correct ratios in a short amount of time. There are a lot more types of bacteria than aquarists realize in a typical SB and some take a good while to repopulate. If you have sufficient LR then the bacteria contained in and on it can help 'take up the slack' during the SB replacement process, but I'd definitely take the slow approach if you are planning to replace most, or all, of it.

My SB is about 80% filled with 16 year old aragonite. The only replacement has been for replenishment due to gradual substrate dissolution. Weekly deep vacuuming with my WC has kept it fairly clean throughout the years.

Good luck!

 

[GroktheCube]

Thanks. I'd say I'm about 2/3rds done now. I've been removing a small amount every couple days. So far, so good. Hopefully I'll be done by the end of next weekend.

I thought vacuuming during WCs was keeping mine clean too, I was quite mistaken! This is after about 10 minutes of settling.

 

[Nano sapiens]

Thanks. I'd say I'm about 2/3rds done now. I've been removing a small amount every couple days. So far, so good. Hopefully I'll be done by the end of next weekend.

I thought vacuuming during WCs was keeping mine clean too, I was quite mistaken! This is after about 10 minutes of settling.

I WC 2x/week and vacuum a different area each time. It's easier in a smaller Nano tank than a larger sized tank.