It's a great product, once you understand what it is, how it works and, more importantly, what it is not. For the right application, it is a great product.
First off, what is it? It is NOT what it is claimed to be in marketing. It is a silica based sand, absent of any soluble calcium or alkalinity and far all anyone can tell is sand mixed with miracle grow, or flourish nutrient tabs.
I have been in this hobby for over 20 years and remember when this product was relatively new. Leng Sy is a pioneer in our hobby and knows what he is doing, but he grossly took the wrong approach on his marketing and shot himself in the foot. He set the bar in this hobby for a snake oil salesman. Which is too bad because it is a great product for the right application. If you ever get a chance to meet him or talk to him, he is extremely knowledgeable regarding the hobby, but I also found him arrogant and willing to double down on the false marketing.
So, to be clear, it is not a miracle and it is not ocean mud...
So what is it and what is it good for?
Basically, it is a finely graded refugium substrate. What it does it is creates an anoxic layer and the bottom of the sand for complete nitrification to occur within your sump. It is a remote DSB, but existing before the term DSB was trending and does so within only 1-inch depth. When people tell you how funked it is when they remove it, this is why. When you read the instructions and Leng says not to have more than half an inch of sand your DT (actually recommends none), it is so your DT substrate does not compete with his mud. What it does is sink nutrients in the substrate where they get fully processed. This is great!
With this product, you will maintain 0 nitrates with no matter what you do!...so long as you follow the instructions.
The most important instruction is you have to replace the product (half of it) every year. The reason is the substrate is only 1-inch thick and it fully fouls up after a year of typical use (see responses above mine for verification). This mud is nasty when used! If you do not replace the mud, it will reach full saturation and will no longer adsorb nutrients from your tank...in fact may be leaching them back in.
So where do I recommend this product? For large fish tanks, this is a great product as you will have virtually no nitrates. Also helpful for soft coral tanks and/or LPS if you maintain the tank on the dirty side.
Where I do NOT recommend this product is for SPS and/or ULNS. The problem you will run into this the substrate sinks all nitrates and you will not be able to fully utilize the pro-biotic approaches. Also, with the lack if nitrate, you will struggle to manage phosphates with carbon dosing...which is why Leng requires you to use GFO along with his substrate.
Regarding the skimmer, I run mine only part time. I get a full cup after running 6 hours. Right now, I am skimmer less and have been for about a month and will stay that way....until I can fix my gate valve
I do not understand what the mud has anything to do with running your skimmer. You can skim with the mud...or go skimmerless w/o the mud...so it is a moot point. Make your decisions on mud and skimmer independent of each other.
Regarding nutrients in the mud...no idea. I grow chaeto and caluerpa, none of which depend on the substrate for nutrients. My guess, as mentioned above. I do agree with the suggestion that this would work great with mangroves...but I don't have any so I leave that to others.
So in summary, if you have a high nitrate problem, this product will solve it. If you have a coral coloration goal, this product will work against you. And remember, chicken always return to roost, so if you use this product to sink nutrients, you will have to remove it before it hits saturation...about a year.
