There has been a large amount of research ongoing in the last few years that suggest Ammonia Oxidising Bacteria (AOB) are not the key microorganisms responsible for the majority of nitrification in aquarium filters. It is actually Ammonia Oxidising Archaea (AOA) and and these Archaea have a wide tolerance to pH.
If Archaea can operate at lower pH levels then it would stand to reason kH would be relatively low too if not near depleted.
From the studies I have seen, it would appear that AOB are more prevalent at higher ammonia loadings such as is found in wastewater treatments scenarios. This bacteria do use the carbonate hardness but there is no evidence to suggest that the AOB can’t also use co2 as their inorganic carbon source like the AOA.
The studies that show AOA have ammonia loadings in the micro grams. It is possible that fishless cycles encourage the growth of AOB such as are found in wastewater or a whole other suite of microbes for that matter which could be why the cycle stalls when ammonia loading is higher and the KH is used up. AOB also prefer ammonia as their total N whereas AOA are shown to favour ammonium.
The point of all this is to say that the work of Dr Hanovec and the notion that nitrification stalls at certain pH and KH levels is outdated or perhaps based on data from wastewater treatment and what happens in aquarium filters is completely different. There fishless cycles in my opinion and to be honest from day one have always been a pointless exercise. Dr Hanovec himself has indicated that production methods have changed over the years.
We need to ensure we are moving forward with regards to the science and be careful that we do not continue giving out outdated information regarding the cycling of the aquarium or how certain parameters impact the system.
One thing is for sure is that both AOB and AOA cannot oxidise without the presence of oxygen and therefore this in my opinion is the most important metric.
If you are worried about KH you will need to spend the money on crushed coral and leave a bit in your filter. This should almost indefinitely last and put your mind at ease.
From someone who performs very irregular water changes with KH depleted water (rain, RO) I know from recent information I needn’t fear the old tank syndrome effect. I keep soft water fish in soft water and an abundance of very healthy plants which are fed at the substrate level and with fish and fish food. This is real balance.
After reading your post, I really do think that the Aquafina might have changed the hardness of the water when I topped off the tank after the levels went down due to testing and evaporation. I checked online and saw that they use RO to purify the tap water that they sell.
I've kept fish on four separate occasions and have to say I was pretty bad on them. First time was when I was a kid and won a goldfish at a fair. My father got a tank for me, either a ten or a twenty gallon I think. My uncle took care of the tank. I remember us going to the fish store every couple of weekends and getting new fish like they were some kind of toys. I believe my father asked the people at the store what they needed, so we did the best we knew how since there was no internet back then. My uncle used to empty out all the water and refill the tank with new water when we "cleaned" the tank. I also remember wanting to reenact a Thundercats episode with my toys and the real fish in the tank and waiting until only my mom was home to do so. The fish soon died after that, so that was my fault as a kid.
We never replaced them because I guess I lost interest, or maybe because my uncle moved out and my dad didn't want to do all the stuff with the tank
Next time I got fish was in my early twenties. We did have the internet by that time, and I did do some research. I vaguely remember seeing something about the nitrogen cycle, but didn't want to wait that long. (I wanted the fish to keep me busy after me feeling bad over a girl I liked.) I saw the quickstart that said you can add fish immediately so I used that. I also remember the tank was a twenty gallon because I read that that's the best tank size for a beginner, so I guess I was trying to do the right thing. I got two orange fish with the black swordtail. The tank unfortunately had a leak, so I had to get a new tank.
Here is probably my most egregious mistake as a fishkeeper. I got an acrylic 2 1/2 gallon hexagonal tank because I knew it wouldn't leak (
something like this, except I believe it had a hood with a light). It had a grate that went underneath the gravel and a tube with an airstone that I thought was a filter. The swordfish soon died and I got two goldfish to replace them. They actually lived 2 1/2 years in those cramped conditions.
About a year after they died, I got a betta that I kept on my desk at work. The "tank" was actually only a 1 1/2 gallon travel container (
sort of like this). I can't remember if it came with the gravel and plastic plant, but I figured it was good enough for a betta since they kept them in those little cups at the store. I think this "tank" also had the grate and airstone in a tube combination. The betta actually lived for over a year, maybe almost two. I remember taking out the plant because I wanted to see him swim around. I should have done my research on that. I did not know that he needed a hiding place to feel comfortable. And I knew from my first tank as a kid that he should probably have a heater but I never got one because I sat by the heating in the office.
I guess I wrote all that down because I want to make sure that I'm doing the very best for my fish this time around. We may not need to do a fishless cycle anymore, but I am uncertain if I can do what's best for the fish like that.
Thanks for your scientific information. I learned a lot and will be much better this time around!
