Yeah, in the 75, 55 and 20 gallon tanks I completely broke down everything including filters, washed everything with tap water and in some cases vinegar and H2O2, and let most of it get dry. The clay in the BCBs and plenums was the only thing capable of eating ammonia, which it did immediately. In my 135 I took out the wet/drys and replaced all the media in the Rena Filstar canister. I put a BCB bag in there, fresh filter floss, some homemade 'chemipure' and replaced the old sponges (they were at least 10 years old anyway). I also removed 3/4 of the gravel and all the decorations, most of which got dry as I did a massive water change and deep clean on the tank and then put in a small plenum (just used a 55 gallon UGF because it was on sale for $25 bucks on Amazon), but without clay, before putting it all back in and replanting. So in there a bit of bacteria may have survived, but for the most part those enormous BCBs and the bag in the canister got all of it. I converted the 135 a couple months before the other 3. All had fish in them, though not that many and I've added several since.So you are seeing 0 nitrates? Most likely because the clay is absorbing the ammonia before it gets converted?
I was fully prepared to do daily water changes for a while, but I stopped getting readings for any nitrogen compounds on my test strips and the water looked great after everything settled. I didn't trust that, so I broke out the test kit (which I hate doing) and got the same readings. This kept happening and I just checked every day, but left it alone for the most part. I converted the other after about 2 months (maybe like a week less). I added more plants, both in and out of the 135 and the plants in the tank didn't really melt much and acclimated quickly. Since then, one of the cichlids (when I find out which one it is, I'm gonna...) has decided they like to eat elodea roots, so those plants are now struggling in the 135, but everything else looks great in there. Minor algae on the plants in my 55 and 75, but plenty of new growth and green popping. The 20 gallon only has the plenum and an HOB for mechanical, I am getting more hair algae in there than I care for, but it also definitely has the strongest light/square inch by far, so I'm pretty sure that's the issue in there. Plants have been growing and spreading and shrimp have been growing and breeding. I haven't done a water change in that tank really. I use a python and usually will suck out a tiny bit before topping off, just so the hose doesn't blow air in the tank, but that's it. The others I've done a handful of 25% or less water changes on since switching over and I did about 30% when I got back from vacation.
So now, even though regular BB is certainly built back up in the tanks and power filters that run mechanical and chemical, the clay is still grabbing all of the ammonia, or enough of the ammonia that even if a little gets converted to nitrates by the 'mechanical' filters, the plants are going strong and are using them all up. I did have a reading for <5 ppm nitrates in my 20 gallon (again, no BCBs in that one, or pothos) when I got back from vacation, but I know I left way too much food for that tank for my sister (or rather somehow didn't consider that she wouldn't be around to take the leftovers out until the next day) to feed while I was away. I didn't add food to it for a few days when I got back, did a top off and the test strip came back 0. My guess is the test kit would still register a tiny amount, but I'm not worried about it enough to check.
I have no way of knowing whether the BCBs and plenums are actually doing what they are advertised to do by Dr. Novak. I am assuming they are, because I believe I'd be getting some kind of leeching at this point if they weren't, but I don't know that for sure. I keep tanks that border on or step over the line of overstocked (except the shrimp tank, which is the one that got nitrates, lol), so they've soaked up a lot of ammonium in the past several months. I've been impressed enough so far, that I'm very optimistic for the long term and just set up my 10 gallon using just a plenum and an old school air powered corner/box filter. However, even if the BCBs don't work long term, I will continue using them as cost effective 'short term' media. It's not just the nitrates, my water has been extremely clear and clean (never had any bloom at all) and the fish have been very well colored and extremely active. Juvies have grown at good pace (not record breaking, but healthy), even without constant water changes, and colored up younger than usual. Plants have also grown better than my brown thumb usually manages, especially the rooted ones (at least the ones that cichlids don't eat) which I think is due to the combo of clean water and the plenums feeding them. I'll figure out the algae soon enough and the shrimp colony expanding should help more than it hurts.
Sorry this was so long, but I wanted to give a full description of my experience so far including the things I'm still in 'trust but verify' mode on and the additional help the system is getting from plenums and plants (though I've done pothos and aquatic plants for years and while it helped a little, I never saw this). I still test the water with test strips at least twice a week (daily or nearly the first few weeks) and was breaking out the test kit every week at least at first, but have slowed down on that as the test strips seem to be accurate enough that I'd notice any spikes. I did use it last week when I got back from vacation, which is when I saw the minor nitrates in the 20.
Each tank's filtration, all have at least some plants in them, but only the 10 is 'heavily planted' at all and it doesn't have fish yet.
135 - 35 gallon sump with 2 milk crate BCBs, run by 2 pondmaster Mag 7's (probably run about 800-1000 gph combined), Rena Filstar XP3 with BCB bag, chemipure and mechanical. water bottle filter running just mechanical with a maxijet 1200, 55 gallon UGF for plenum. Pothos and peace lilies growing out of tank.
75 - 3 foot planter sump with 2 planted BCBs (12x5x3.5 each) run by a maxijet 1200 (head only about 10 inches). SunSun 302 for mechanical and chemical, water bottle filter just mechanical MJ1200, full sized UGF with clay included plenum. Pothos growing out of tank.
55 - 2 foot planter sump with 1 planted BCB, MJ1200, head about 1.5 feet. Fluval 305 for mechanical and chemipure. AC50 for just mechanical. full sized UGF with clay included plenum. Pothos growing out of tank.
20 - 20 gallon UGF for plenum with clay. AC50 for mechanical and chemical. Medium planted. No pothos
10 - 10 gallon UGF plenum with clay, corner box filter, 'heavily' planted, will have pothos.
Obviously overkill on the first 3, but I've had all the filters for years and used to have more tanks. And I like my little water bottle filters for water polishing because they're so easy to switch out the floss.