yes, but I'm looking in to replacements. I don't think it's pellets that are the problem per se, but how they get used and how little their mode of action is understood. There are definite red flags about them - first and foremost of which being that no one has even the slightest clue about how much of the polymer makes it in to the water column, or even where the majority of the nitrate reducing activity is taking place (in the reactor, or in the tank using the carbon that dissolves/breaks off the pellets?). The fact that people report it takes weeks to see a reduction in nitrates has always made me suspicious - I've run the reactor at a slow tumble with not a lot of water pass through, and the bacterial mats that form inside of them grow lightning quick. The entire column of pellets can be fused in a thick, white, microbial mass in as little as 48 hours. Alternatively, when the pellets are tumbling fast enough to prevent clumping, there is usually zero build up of bacterial mulm anywhere in the reactor. Also, it's not uncommon for people to add pellets to their system and within days see the entire tank turn in to a lush cyano garden. I've always wondered if that means that the bulk of the 'work' pellets do is actually taking place inside the water column using carbon that's sloughed off, but you'd need to do some really sophisticated organic carbon analysis (that to my knowledge no one has ever done) to know for sure.
If I could find a nitrate control method that made sense with my setup that was not pellets I'd switch, but my tank is too heavily fed to not have some sort of intentional nitrate control system in place. Adding a gigantic refugium or remote DSB is physically not an option and I don't really have any space for something huge and bulky like a sulphur denitrator or an ATS. The only other 'proven' method is liquid carbon dosing, which is basically the same thing with a different delivery method but I don't know I'm ready to commit to switching. Dosing it in liquid form has the benefit of giving you precise and immediate control over how much carbon you're adding, but at the end of the day no one really understands the full spectrum biochemistry of carbon dosing anyway. I might end up switching to vinegar or vodka/vinegar dosing at some point.
In the meantime, I'm running my modified reactor with 10% the pellets it used to have before I increased the effluent pipe diameter, and I've restricted the flow through it significantly. I'm also monitoring my nitrates and will only add small amounts of pellets if the nitrates continue to climb over a period of weeks. This seems to be a safe level, but then again maybe pellets had nothing at to do with the what happened in the first place.
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