Dark Substrate

[Fishstein]

There is a much better much cheaper option for you. When I was looking for the same type of dark substrate, several Aquatic Plant Central members suggested low cost Soilmaster Select, about $20 for a 50lb bag, as an excellent dark substrate. They said it won't change water chemistry or leach nutrients into the water column. Soilmaster Select is so cheap because it's sold as a bulk clay for sports fields like baseball fields. You can usually get it from home improvement centers and building suppliers. Just look it up.

 

[Maximumbob]

One of the places UK people can get onyx sand (amongst other planted tank substrates) is Aquaessentials

 

[Snape]

Ignore the slightly poorly gourami, this is onys sand in my tank.

If you'd like more pics let me know

Mark

 

[Fishstein]

Also, if you require any extra buffering capacity, you don't need to get that from your substrate - you can achieve the same, actually even better result, by placing some crushed coral in your canister filter and using it as biological filtration media. It does a great job for me in my XP3.