Different sands

Certainly play sand in the UK has no coral or shell in it. The reason its "safe" is the producers expect their customers to eat it and land on their knees etc.

No fish that I am aware of eat sand or digest it. The issues with bottom feeders is potentially cutting or scratching their barbels and some fish (like corys) filter the sand through their gills.

If you are comfortable with what you use there is no reason you can't, although be aware that coral and shells could affect pH

 

Here in the US, play sand typically comes from land deposits and doesn't contain shell or coral. However, there may be some play sands (white ones come to mind) that originate from beaches.
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For a planted tank you really want a somewhat coarser sand as fine sands tend to pack too tightly, inhibiting root growth. I also think that a coarser sand is better for beneficial bacteria and burrowers like Malaysian Trumpet Snails.
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I'm using pool filter sand in a couple of my tanks and although some feel it's too sharp, I've had Cory catfish for many years with no issues (barbells just fine). As a matter of fact I recently saw a video (Aquarium Co-op) of hundreds of Cory's in the wild where the river substrate was a very sharp gravel. Fish have of way of surviving in some pretty hostile areas!

 

Ok, here we go....(IMO for all of this)

Play sand in the US is completely safe for any tank you have. It is cleaned, and has to be, because it has to be safe for kids to put in their mouth.

I use play sand in all of my tanks and have used it for over 5 months now. It looks great, and its cheap. It is also really good for any aquarium plant. (I have about 100 stems of Anacharis in my 10g betta tank right now. Some floating, but most of them growing in the sand.)

As pool filter sand might be classified as "Cleaner", or "More safe" in the long run it really isnt. Most pool filter sand is more on the white side, and can stress out your fish. And even if fish can survive in the wild with sharp substrate, it doesn't mean we should give them that. As aquarists, it is our duty to give out fish the bets possible home.

Back to the OP you mentioned wanting to have fine sand? Play sand is very fine. As you can find small grain pool filter sand, the sand you buy in stores usually have large grains.

Overall I think you should get play sand.

(P.S. I bought my 50lb bag of play sand for just $5 USD.)

(P.P.S. No hate @AbbeysDad, just IMO. )

 

This caught my attention, so I watched the video. It is very misleading. If you look carefully at the river substrate during the video you will see it is primarily sand. The handful of "sharp" particles is not the substrate, but scattered here and there. There is no way any Corydoras is going to even attempt sifting that through their gills.

All species of Corydoras live over a habitat substrate that is either sand, mud, or a combination. There is one exception according to Ian Fuller that does live over gravel, and I can't remember which species, but it doesn't matter.

And the issue of sharpness has less to do with barbel loss than it has to the inherent trait of fish in this family to sift the substrate through their gills. This is why they live over sand and mud, and why we provide smooth sand for them.

 

Just for the record, the pool filter sand I've used for several years now is just as tan and natural as nearly any play sand and although purported by some to be too sharp, it sure doesn't seem to be....and my 10 year old Cory's are just fine with it.
Also....
1) I didn't invent using PFS substrate as it's been used by many hobbyists [especially in planted tanks] for many years now.
2) I attempted to use some big box store play sand a few months ago. Put some in a 5g bucket to rinse clean. There were more dust like fines than coarse sand particles - about like trying to clean dirt/mud, so most of it just got dumped out...so I put pool filter sand in the 37g instead.
(Just my opinion)

 

Did you make sure to get the sand that said, "Cleaned", or "Processed" on the bag?
If you didn't, then that is the reason why your sand was very muddy. When I got my sand, I had to wash it just a little bit to get it cleaned.

 

Sakrete All Natural Play Sand, prewashed & screened.