I'm on day 5 of fishless cycling a new 75. (I used a bottle of Dr Tims nitrifying bacteria on day 3)
ammonia is 0.5 PPM
Nittrite is 5.0 PPM
Nitrate is 80 PPM
PH is 8.1
GH is 8
KH is 9
Is my next step to add mor ammonia to get it up to 2.0 PPM? Do I need to also do a water change to lower the Nitrates? Or do the Nitrates not matter because there are no fish?
Thanks!
I found that ammonia-dosing fishless cycling is done best through a particular method:
1. Dose ammonia.
2. Add nitrifiers, as much as you like/can.
3. Measure ammonia and nitrite every 24 hours.
4. Once ammonia and nitrite reads zero, if it took more than 24 hours since dosing ammonia, re-dose ammonia and repeat from step (3). Otherwise the tank is cycled.
You can opt to dose 1, 2, or 4ppm ammonia. Well you can opt for any amount of ammonia, but those three numbers are most common. 1ppm is basically what is expected to be produced daily by a well-fed, fully stocked tank, so it should be enough for most tanks. 2ppm is for heavily fed tanks. For example in my 10 gal, I feed it eight times with quite a few pellets, so I would be aiming more for 2ppm than 1ppm. 4ppm is kind of a stretch goal, a buffer just in case something bad happens - to handle extra ammonia produced by a fish or plants or whatever dying for example.
There were previously a lot of debate of whether to constantly keep ammonia at a certain amount versus letting it get to zero, and also whether to re-dose ammonia when both ammonia and nitrite reach zero, or if only ammonia reads zero.
To answer the first question, turns out it does not really matter much - so long as there is ammonia, it will promote the growth of ammonia-oxidizers. There was also worry that the nitrifiers would starve if there was not a constant source of ammonia, but again untrue - ammonia oxidizers can go for weeks to months ammonia-starved before even going dormant, let alone die off. So there is absolutely no worry about letting ammonia go to zero. To answer the second question, while certainly ammonia may need to be continued to be provisioned for ammonia-oxidizers to continue to multiply, the rate-limiting step is establishing the colony of nitrite-oxidizers, so that's the more important step. But! If one keeps dosing ammonia, it can just keep on raising nitrite, and that poses multiple problems. First, a high enough level can actually inhibit nitrification and thus the cycle. Not 5ppm that Dr. Tim says though, I have seen enough examples of myself and others getting nitrite way higher than 5ppm and not inhibiting growth of a diversity of nitrifiers. But there will be a point, so far I am guessing about 50ppm or so. Not 100% sure on that though. Second, a really high nitrite concentration most likely mean one need to grow far more nitrite-oxidizers than needed to bring that nitrite down, hence also slowing down the cycle.
It is therefore desirable to wait until both ammonia and nitrite to reach zero before re-dosing ammonia.
The second question is, how many times to re-dose ammonia? As many times as needed to get ammonia to be converted fully to nitrate within 24 hours, because that's the expected timeframe one'd want for a fully stocked tank.
Another question is, well, I'll be slowly stocking the tank anyways, do I really need to establish 1ppm, 2ppm, or 4ppm ammonia/day oxidation rate from the start? No, you don't, but since we are at it, why not? It does not take much more time, and saves a lot of headache later.
Hope that helps!
