Mixing fine and coarse substrates?

[morganatlanta]

For my new 120 gallon system, I'm looking to use Seaflor Special Grade reef sand-- at least mostly. Since the Seaflor grain size is pretty large (1-2mm) would it make sense to mix in a bag or two of finer grained sand? I want the larger grain size for a jawfish, but it seems like maybe a mix of sizes including some finer grains might be better than uniformly coarse. Any thoughts?

 

[dakota9]

I've been mixing substrates for years with no ill effects linked to the practice...... Don't read what I didn't write! I've had many ill effects over the years, but nothing directly linked to the substrate choice.

 

[lilrobb]

Put two samples of these sands in a glass and shake it a couple of times.
All the coarse stuff will be on top - all the fine down, it's a physics effect that escapes me right now.
Mixing substrates only works if you (or any fish) will absolutely not disturb the sandbed...

 

[ichthyoid]

LilRobb;588002 wrote: Put two samples of these sands in a glass and shake it a couple of times.
All the coarse stuff will be on top - all the fine down, it's a physics effect that escapes me right now.
Mixing substrates only works if you (or any fish) will absolutely not disturb the sandbed...

FWIW- I believe it's due to a higher 'effective viscosity' for the larger diameter particles, Robb.

In nature, most substrates consist of distributions of particle sizes, including seafloors. The good news is that there is not a lot of 'perturbation', or external energy applied to speed up the process of stratification, or separation by size.

 

[lilrobb]

"Reverse buoyancy in shaken granular beds" or the "Brazil nut problem"...

 

[morganatlanta]

As in the Brazil nuts always come to the top and you have to dig for the hazelnuts?

 

[misu]

MorganAtlanta;588120 wrote: As in the Brazil nuts always come to the top and you have to dig for the hazelnuts?

yeap, so if you don't want a mess of nuts in your tank don't mix the sand