Dear ageber:
I do feel that black sand generally shows off the colors of seahorses and macroalgae better than white sand, and I find that fine grained oolitic sand generally works best with our amazing aquatic equines.
When it comes to live sand, many seahorse keepers report good results using either the Arag-Alive Indo-Pacific Black Sand by CaribSea or else the CaribSea Tropical Isle Tahitian Moon Black Sand. You can obtain them online from Premium Aquatics (http://www.premiumaquatics.com/) and a number of other sources, and either of them should work great for your new seahorse setup.
For best results, stick with a relatively shallow bed of sugar sand like the above that is between 1/2 and 1 inch deep rather than trying to mix a gravel base with a covering of fine sand.
Best of luck with your new 90-gallon seahorse system, sir!
Happy Trails!
Pete Giwojna
Ocean Rider, Inc. is an Organic Hawaiian-Based Seahorse Aqua-Farm & Aquarium that Follows Strict Good Farming Practices in Raising Seahorses and Other Aquatic Life.
