Onyx Sand is a naturally dark gray sand that perfectly complements and enhances the appearance of any aquarium. It provides not only iron and other minerals but supports optimal KH levels for freshwater planted aquariums. Being carbonate rich, Onyx Sand provides an advantage to any plants able to utilize bicarbonates. Although ideally suited to planted aquaria, it may be used in any aquarium environment. Onyx Sand is most effective when used alone as an integral substrate bed, but it may be mixed with other gravels. Gravel modifiers such as laterite are not necessary. Onyx Sand is not chemically coated or treated but does have a slight buffering capacity that may raise pH by 0.1 - 0.5 pH units (depending on source water characteristics). Onyx Sand is good for the life of the aquarium and need not be replaced.
This stuff has no business being called "onyx" sand. It's more the color of broken, beaten asphalt one would find in a city schoolyard. It's impossible to ever rinse clean, and what's worse for tanks where you are trying to keep a low pH and hardness - it has a noticeable buffer effect. I noticed little to no significant benefit to the plants and my rams and angels sure didn't appreciate the higher pH. Considering the expense of the product, that made it even more of a mistake to buy as far as I am concerned. I wouldn't recommend this stuff. There are such better choices. I ended up replacing it with black sand and root tabs. Haven't looked back since.
This sand is a great substrate for planted aquariums. It provides many of the needed nutrients and is easy to aquascape. It isn't as dark in the tank as it appears in pictures though. The color is more gray than black.
This sand is absolutly great. Easy to rinse, and great for plants. It brings out the colors of my fish, and is just the perfect sand substrate. It would be cool if they had this same product in white. Other than that, I still love the darkness that it brings but it also lights my fish up.
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