Substrate Question: Sand Sifting Species

I would like to know from those with sand sifting species what you use for substrate. At the moment I'm thinking of making my own mix using play sand, silica sand, and crushed coral/crushed oyster shell.

Does anyone used (or presently using) either of the last 'ingredients'? A friend mentioned that I may not want to use the oyster with gill sifters (eat sand, expel out gills) because it may cut the rakers. Sounds like a legitimate concern so I'm looking for feedback if this is likely - if so I'll gladly avoid it.

Is crushed coral safer than oyster shell - and is it safe enough for gill sifters?

Right now the only real sifters I have are the Lethrinops sp. "Deep" Malopa - and they are more of the 'eat-n-spit' sifters, not running the substrate through their gill rakers (but this could be because of the gravel I use). I want to make sure I have a substrate that is sifter-friendly.

An older video of them feeding.

https://www.youtube.com/watch?v=c93BNxvIgDI

In Mississippi they use oyster shells instead of gravel to lay down on dirt roads. I wrecked my bicycle on one of them and it was not a pretty sight. Coral has always seemed sharp to me also. I suppose if the sand is crushed well enough it wouldn't be a problem but why take the chance. You could put the oyster or coral in a nylon sack and stick it in your filter somewhere if your looking for some buffering.

Personally I would not use crushed coral/crushed oyster shell. As you mentioned, these fish filter the sand through their gills to look for food and anything remotely sharp has the potential of injury.
I use fine silica sand only for my sand sifters. I would also recommend not to use play sand. The play sand is very fine and light, which makes it a PITA to vacuum all the dirt from the substrate surface. The fine sand sucks right up and down the drain. The silica sand is quite heavy and stays where it belongs, in the tank.
If you want to use the crushed coral to buffer your ph, consider using some limestone rocks. They look great and perfecly do the same job.

Well the general consensus from the multiple forums has been pretty much the same. Crushed oyster shell is a definite no - the pieces are likely to be sharp and a high risk addition.

Crushed coral is might be okay but could also be sharp enough to hurt the gills - so to be safe it is no longer an option as well.

Just to clarify for some, the crushed coral/oyster shell wasn't being added to change water chemistry - it was only going to be added for decoration. The fact that it would act as a buffer didn't even cross my mind - but I'm glad people brought it up. I don't think I want to mess with the water chemistry more than I have to even if my pH is a bit low for Rift's (7.4).

As a decor substitute I think I'll get a bunch of Malaysian Trumpet Snail shells and add them to the sand mix. I'm not worried about them hurting my fish as there is a significant amount of them in my gravel mix from past populations and it doesn't haven any effect on the sifters.

buntbarsch wrote:I would also recommend not to use play sand. The play sand is very fine and light, which makes it a PITA to vacuum all the dirt from the substrate surface. The fine sand sucks right up and down the drain.

Klaus - I siphon my water into buckets before getting emptied so I am not real worried about the lightness of the play sand at this time.