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I was looking for some fine white sand at the LFS and the only one they carried was Carib Sea Marine fine white sand. The bag says it's for freshwater aswell since it's not supposed to alter ph, but is this safe for corys? Any one use this for their corys?

It is pure silica sand. Completely inert in aquarium conditions but may dissolve when exposed to hydrofluoric acid but so would your glass. They are the same substance.
I would check my local swimming and hot pool supply store and take a look at their filter sands. Much cheaper and as safe.
Careful about the thickness of a fine sand substrate. Water circulation through sand is lower the smaller the particle size. I generally use fine sand in very thin amounts. Poor water circulation can lead to anoxic conditions which promote bacteria growth which can cause blacken areas and production of H2S gas, very toxic and readily soluable in water. A sponge filter equipped with a powerhead is useful as an aid to promote sand from becoming compacted and nearly all catfish like a brisk current.

As Larry says, be VERY careful on sand thickness- I used about 0.6" last year, stirred it well every day, and after about 3 weeks lost all my 6 [iCorydoras similis][/i], plus a juvenile Brochis splendens, within 3 days of each other. I've got friends that successfully use very thin layers of sand in tanks, but it seemingly has to be really thin.

I usually use a layer >1/4 inch when it is fine silica sand. I pot all rooted plant in FloraBase. This does limit ambitious aquascaping but the benefits of having even a very thin layer of sand in Catfish tanks, especially fry tanks, has made it worth it for me. I actually just use FloraBase on the bottom, too. It is attractive and has some ability to attract fine particles from suspension due to electrostatic attraction.
It makes an excellent deep substract but make sure you have plenty of money budgeted for substrate if you go with deep layer. Deep to me means ~3-inches.

I read silica sand was a sharp substrate so not appropriate for corys. Have you guys been using silica sand without problems?

I have used Carib Sea tahitian moon sand with my cories and no worries and I have also tried mixing Carib Sea Moonlight white with tahitian moon sand. The moonlight white is too fine like powder I won't be using it anymore unless it's a light mixture of that to way more black tahitian moon sand.

But I have had no adverse cory reactions.