# mixing gravel sizes



## curiousburke (May 27, 2011)

Hello All,
I'm fairly new to fish keeping and it seems the more I learn the more I spend in modifications to my setup. I currently have the standard petstore pea sized gravel in my 46 g tank with a school of catfish and a pair of kribensis as bottom dwellers. I'd like to get some smaller gravel for them since I've read they digg it  I'm thinking the caribsea peace river gravel, which is 1 to 2mm on average. 

What do you think about mixing that in with my current gravel or at least some of it?

All opinions are appreciated,
Mark


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## AbbeysDad (Mar 28, 2011)

Although you can mix gravel sizes, I'm not a fan of pea sized gravel as it allows too many nooks and cranny's for food particles to fall down into, out of reach for the stock. I don't know how well mixing in a smaller gravel will reduce. Just me, but I think I would opt for a smaller gravel and replace the pea sized stuff altogether.


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## curiousburke (May 27, 2011)

I don't know fish, but I do know something about granular materials from my trade. The air space in the gravel should actually be lass with a mix of grain sizes because the smaller pieces fill in the voids.

http://www.co.portage.wi.us/groundwater/undrstnd/soil.htm



AbbeysDad said:


> Although you can mix gravel sizes, I'm not a fan of pea sized gravel as it allows too many nooks and cranny's for food particles to fall down into, out of reach for the stock. I don't know how well mixing in a smaller gravel will reduce. Just me, but I think I would opt for a smaller gravel and replace the pea sized stuff altogether.


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## AbbeysDad (Mar 28, 2011)

curiousburke said:


> I don't know fish, but I do know something about granular materials from my trade. The air space in the gravel should actually be lass with a mix of grain sizes because the smaller pieces fill in the voids.
> 
> Soil Properties that affect Groundwater


Challenge is maintaining a uniform mix - like gravel and sand, you think of it uniform, but it often finds it's own place so that the small particles don't always fill in the voids.
Try it and see how it works - nothing ventured, nothing gained.


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## curiousburke (May 27, 2011)

Do you think the Cories and Kribs would still enjoy digging in it if it had the larger grains, or will they really only dig in the fine stuff?


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## sik80 (Mar 16, 2010)

the small particles will work thier way to the bottom eventually, so it'll be hard to maintain the mixture. It might be possible to maintain 2 areas in the tank with different gravel types using some type of divider; this could look unattractive unless you cleverly hide the divider


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## Byron (Mar 7, 2009)

From my experience, the gravels will mix and the smallest grains fall to the bottom and the larger will remain on top. I notice this even with my same-sized gravels and Flourite which has some very small sand-like particles and some 1-2 mm sized particles; the smaller are at the bottom, always. You can clearly see this along the front glass.

We sometimes forget that in a healthy balanced aquarim, water is constantly flowing down through the substrate and back up again, heated in the substrate by the bacterial processes occurring there. This convection or thermal flow is I suspect why the substrate shifts. As it is not static, the otherwise-logical mix of small/larger grains does not occur. And of course, there are plant roots burrowing through, and perhaps Malaysian Livebearing snails; both of these cause substrate shifting, which is why they are so useful.

I would replace the pea gravel with either fine gravel (1-2 mm grains) or coarse sand. As someone mentioned, two types of substrate mixed usually does not look "natural" but like two things mixed.

If the catfish are Corydoras, fine gravel works well, or sand. Except for the dwarf species which seem to do better over sand, which probably is not surprising.

Byron.


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## curiousburke (May 27, 2011)

okay, sounds like replacing is the way to go.

Does anyone have experience with the caribsea gravels. They have 1-2mm peace river in a wet biologically active package and in a dry clean form. If I can get the wet cheaper, is there any disadvantage. For example, could it upset the balance with the bacterial in my canister filter?


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## 1077 (Apr 16, 2008)

curiousburke said:


> okay, sounds like replacing is the way to go.
> 
> Does anyone have experience with the caribsea gravels. They have 1-2mm peace river in a wet biologically active package and in a dry clean form. If I can get the wet cheaper, is there any disadvantage. For example, could it upset the balance with the bacterial in my canister filter?


I should think the dry would be cheaper with respect to shipping costs for it would be lighter than the wet which would be heavier, possibly due to more water.
So long as the canister's bio-media is preserved (kept wet during substrate change)you shouldn't have any issues.


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