Onyx Gravel, 7 kg / 15.4 lbs

I'm about one week into having this medium submerged under water with the water filter running (I let the plant seeds sprout and root well before raising the water level above the substrate). So far I've experienced no ill effects or cloudiness, the PH has been stable even though it didn't buff the PH, KH, or GH nearly enough on its own for most African Cichlids. I used half tap water and half RO water in my 30gal, ran it for a few days, and came out with a PH of roughly 6.5-6.8. I've yet to add my cichlid, but will update my review accordingly if something bad happens relative to the substrate.Oh, and wash it with a water hose and a strainer bowl half-way full until the water no longer looks cloudy. It will never be 100% clear, but you will notice when the runoff stops getting any clearer. No cloudiness issues for me this way, even during filling.

The product is fine. I was just expecting the color to be black to match my existing substrate, but it really is grey.

The color of the gravel on the bag and Seachem's online pictures are not even close to the true color of the gravel. I was expecting a natural slate-colored stone, instead, I received stones full of white pigment.

Honestly, I almost did not buy because of the reviews saying it has a lot of fine debris. Well, it does—But, I got a half a bag, rinsed it for awhile and it's been great. I can't say it makes a HUGE difference in PH or not, but it sure makes my blue Cichlids pop! Great for contrast, I use it with a black background. See pic :) — Again, if spending an hour 2 pre washing this is a drag I do recommend using something else tho! Cheers😇

First let me say Seachem should be ashamed to refer to this ground up "crush and run" as aquarium gravel. When I wrote to them with that very accusation (stating that this was nothing more than ground up rock used in highway construction) this was their exact reply:"I am truly sorry you are disappointed with our Onyx Gravel. I read that crush and run is gravel mixed with limestone. Our Onyx Gravel is a naturally mined substrate and although it may look similar and may even come from the same quarry, I assure you it is of high quality" Dont you find it interesting that their own sales rep states: "it MAY come from the same quarry" ??? Yeah no kidding. BECAUSE IT IS THE SAME. Where it probably is true that Seachem chemically washes the rock to remove anything harmfull to your fish, that doesnt mean that something porous like "crush and run" will serve as a good substrate in an aquarium. It just simply doesnt work. TRUST ME. Then to add insult to injury they strongly suggest that the Onyx should be washed before using. What they dont tell you is this gravel is very brittle and very porous-- which means it will ALWAYS BLEED PARTICULATE INTO YOUR TANK, no matter HOW MANY times you wash it.As one of the most expensive substrates on the market it is absolutely the worst. Period. Please save yourself the time and trouble of having to totally redo a tank because you bought this crap and ignored what I wrote here. I guarentee that "Black Onyx" WILL BLEED AND TURN YOUR WATER CLOUDY. Truthfully, in my opinion, this "gravel" should be removed from the market. It belongs in a highway bed, not the bottom of your aquarium. I have been setting up and designing aquariums for over ten years, and have NEVER had a problem with any aquarium gravels-- even the cheap colored ones. I currently have ten beautifully clear aquariums in my home, but of course this crap had to occur in my largest one. Try dealing with a 110 gallon tank full of micro-particles bleeding directly out of this rock. Sound like fun to you? It wasn't. I had to pump out the entire tank and start over. I tried everything to clear the water, including Seachem's clarifier, but to no avail. The solution? I went to the Pet Store and bought standard Aquarium gravel. Problem solved. Filled the tank and its been clear ever since.

Its not black not even a dark Gray, But my fish seem to be fine in it.

I used 3 bags of the 15 pound "gravel" I spent almost 100$ on all three and I'm so highly disappointed!!! I thought this product would be great since it is made by seachem. I was completely wrong. Its been four days and its just as cloudy as the first day I put it in. I run a over sized canister as well as two very large sponge filters! Nothing has changed in over 4 days. I highly recommend not wasting your money on this!!! I wish I would have read the reviews first.

I use this for my 5 gallon fluval chi that houses a female beta. I found that if you don't wash it thoroughly, it clouds the tank pretty badly.