Xport Bio Blocks for Freshwater Aquariums were designed to withstand pH ranges below 7. These cubes can also be used in aquariums with a pH above 7. Xport Bio Blocks have the largest surface area out of any media for housing beneficial bacteria. We have been testing this product in our 480 gallon shrimp tank since November of 2018 with amazing results.
I had an undersized filter that was struggling. I swapped out the stock canister biological media with a pack of these. Problem solved.
I am dropping one of these in the back of all my aquariums as a "just in case" remedy or for quick cycling new aquariums.
Not sure how to really objectively test the effectiveness of these blocks. But they are very porous and I don't doubt they do a decent job at harboring beneficial bacteria. The only downside really is that they're a very soft stone and easily chip and fragment, pretty similar to chalk but breaks off in many small chunks if it scraped something even lightly. One of them also seemed to be partially buoyant so it wasn't easy to keep it buried in the substrate while it does its thing, probably due to air trapped in it.