Substrate questions

[ICEEGRL]

Thank you for the pictures! They help.

 

[WhistlingBadger]

Pool Filter Sand on Left, lightly rinsed, Quikrete play sand on the left, highly washed, missing about 30% of the finest material via the washing processes. I wanted to remove the finest grains to facilitate water movement through the sand.

View attachment 139128

I'm guessing you meant pool filter sand on the right?

 

[Uberhoust]

No the pool filter sand was on the left. I looked again because I often get left and right mixed up but it is definitely on the left. I have a five gallon pail of it too on my deck.

The play sand is on the right.

Pool Filter on Port side
Play Sand on Starboard

 

[WhistlingBadger]

So the pool filter sand is actually smoother than the play sand? Interesting. I would have expected play sand to be smoother, but filter sand to be more uniform in size.

 

[Byron]

So the pool filter sand is actually smoother than the play sand? Interesting. I would have expected play sand to be smoother, but filter sand to be more uniform in size.

That puzzles me too...pool filter sand must be rough or it is useless. This excerpt from "Swim University" [link below] describes it.

The pool pump pulls dirty water to the filter, where it passes through the sand, where contaminants get trapped. The clean water flows back into the pool. How exactly does the sand hold onto the icky stuff, while allowing the cleaned water to pass through?​

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Though it’s much too small to see with the naked eye, all three types of sand have a rough surface where contaminants get caught as the water flows past.​

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Over time, the rushing water wears away the prickly surface of the sand, leaving it smooth and round. When you look at sand from beaches with intense waves under a microscope, it’s noticeably smoother than sand from calmer beaches. The same principle applies to pool filter sand, which has water flushed through it for several hours a day.​

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This smoothing is the result of a process called weathering. Ironically the same process that creates sand also wears it down into dust, useless for filtering anything.​

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When pool filter sand is weathered smooth, it doesn’t have any jagged edges to grab and hold contaminants. Your pool may start to look cloudy or require more frequent shock treatment as the filter media nears the end of its lifespan.​

How to Change Pool Filter Sand

Save money, clarify pool water, and keep your family safe from dangerous water-borne illnesses by changing pool filter sand yourself, quickly and easily.

www.swimuniversity.com

 

[Uberhoust]

The filtration process depends on the pore size not the angularity of the fragments. If the particles are all the same size you have effectively a fixed pore size from which you can determine the surface area and depth required for the filter to effectively work. If you have a mixture of sizes and they are angular it is very difficult to determine the overall pore size and settling can occur.

For example if you have a bunch of spheres you cannot pack them close enough to close all the pores. But if you have a bunch of triangular or cubic solids you can pack them together to form an impenetrable mass. The extreme example would be glacial till, a mixture of clay, sand, gravel, cobbles etc, these form impermeable layers to water, but the ocean sand you mention will allow water to flow.

The sand filters are popular because they filter effectively down to a specific size, after which the more traditional paper type filters or disinfectant takes over. The sand filter can be cleaned easily by backflushing the filter media and because the grain size is similar between the particles it breaks apart easily and releases the trapped particles. Angular particles can tend to bind or lock in place making the backflushing more difficult.

This all said you can make sand filters from more angular particles but then the sorting for size has to be tighter. But it is still the pore size that is filtering not snagging debris on angular bit. There are filters that do depend on the angular shape but those are not the type used in pool filters.

For pool filtering sand you want the filter to stabilize with the normal water flow, the objective is not to have the grains move around because that only provides an opportunity for contaminants to migrate through the sand column. Therefor weathering processes are not involved.

I read your links, I would suggest the Swim University one has a little bit of BS in it.

https://courses.cit.cornell.edu/cee4540/pdf/Filtration.pdf

 

[WhistlingBadger]

Yes, I believe weathering occurs mostly from sand-on-sand abrasion, not from water flow. If the sand isn't moving around, it won't weather. Or if it does, it will take a long, long, long time.

 

[Avel1896]

Hey
I always prefer neutral (inert) substrates coz plant substrates end to run through nutrients in +/- 3 years.
I prefer adding stick/ball to roots.

 

[ICEEGRL]

Has anyone used black diamond sand?

 

[Uberhoust]

Are you referring to the sand blasting sand? If so I have heard of people using it but I haven't used it personally. It is a product, I thought, was made from various slags so I was always wondering about heavy metal contamination.

 

[WhistlingBadger]

Has anyone used black diamond sand?

I've used black diamond. Some say it's too rough for cories, but mine have done fine with it for multiple years. Your mileage may vary.

 

[Uberhoust]

I might have to see if I can find a source. Assuming it is black.

 

[ICEEGRL]

Tractor supply co carries it. 2040 is what most people say get. I was wondering if that was the right one for plants and fish or if I should go the next size finer.
it is black and looks nice.

 

[Uberhoust]

I looked for Black Diamond a couple of years ago, but could find any locally, and to order it would mean one of those 2 ton bags. I use carbide grit for other purposes and know how sharp it is so didn't really try too hard to get some Black Diamond. But if one can keep corys in it it cannot be to sharp.

 

[Byron]

Judging by what I have learned from the cory experts in this hobby, any industrial sand used or intended for blasting is too rough for substrate fish. The fact that they may survive for years is not the issue; my cories survived for 15+ years over gravel, but that does not mean they were thriving, as they now are over play sand.