I would not use QuickStart if it were given to me for free. I would not use it if they offered to pay me to do so. I believe I stated this early on in this thread.
Yes it can hurt what you are tyring to do. So it is time for a bit more biology. Bacteria are living things. They can die. When they die they do what anything else organic does- creates ammonia. Because of the patent protections on the specifc bacterial, especially the ones which handle nitrite, they are not in any other starters besides One and Only and SafeStart.
Not all bacteria are the same when it comes to handling ammonia and nitrite. What differentiates them is how much ammonia they need to survive and thrive. The bacteria we end up with in our tanks are ones which can thrive on lower levels of ammonia and nitrite. Aquariums do not produce the levels of ammonia or nitrite that waste water treatment plants handle. As a result the bacteria in waste treatment and in aquariums, though they do similar things, are not the same.
The research shows that when the starter bacteria used are not the proper ones the cycle takes the same amount of time and in the end the added bacteria are mostly gone and have been replaced by the ones which will be there over the years. Even when the ammonia ones are correct, there is still a big difference between what is in sw tanks v.s. freshwater ones.
Grommen, Roeland, Lenny Dauw, and Willy Verstraete. "Elevated salinity selects for a less diverse ammonia-oxidizing population in aquarium biofilters."
FEMS microbiology ecology 52, no. 1 (2005): 1-11.
Abstract
The activity and changes in the structure of the community of the ammonia-oxidizing bacteria belonging to the Betaproteobacteria were monitored in freshwater and artificial seawater biofilters for two months after inoculation with a commercial nitrifying consortium. Both in freshwater and artificial seawater, ammonium oxidation proceeded immediately after addition of the inoculum, although initial activity in artificial seawater was lower than in freshwater. Denaturing gradient gel electrophoresis of the ammonia-oxidizing bacterial community of the inoculum and the freshwater and the artificial seawater aquaria as a function of time showed that initially only one dominant ammonia-oxidizer, closely related to
Nitrosomonas marina, was detectable in all the systems. The fingerprint of the ammonia-oxidizing bacterial community in the artificial seawater biofilters continued to be dominated by this single band. In the freshwater aquaria, in contrast, the composition of the ammonia-oxidizer community became more diverse after one month, with 4–7 new bands appearing in the denaturing gradient gel fingerprint. Since the inoculum is cultivated at an average salinity of 11 g 1−1, it is argued that the elevated salinity selects for a less diverse ammonia-oxidizer community in the inoculum and the artificial seawater aquaria.
from
https://academic.oup.com/femsec/article/52/1/1/481716
I am happy to help you, but not if you are going to do what comes into your mind ot because you got different advice. Further, I never insist one does things my way. That choice is not mine to make. However, I am also not willing to waste my time trying to help if one is going to listen to other advice which contradicts mine. So I will tell you what I have told every beginner in the hobby dealing with cycling and getting help with it. When you hear multiple differing opinions coming from different people, the best thing to do is to pick one person and to follow their advice. Shut out the rest.
That way you will quickly discover one of two things. Either what they say will and should happen does or else it does not. Either way one learns form the experience. If what one does works as planned then they learn how to do the thing so it works out, or, if it fails, they learn what does not work. However, when one tries to listen to differing voices/methods and tries to combine them, one becomes more likely to fail.
So it is up to you if would want to do things as I suggest or if you prefer to listen to other people instead. I will not be upset if you prefer listening to other advice instead of mine, that is life. I am not the only one around who can help and there are usually several good ways to do anything in the hobby.
If you believe you have a better way of doing the cycling or if you have somebody else who you feel is more qualified and experienced to help you, I am happy to back off with no hard feelings. An important part of all of this is not to get confused because there are so many voices out there saying different things.
I do not believe in doing fish in cycling. This is especially true for those new to the hobby. My first tank was a fish in cycle. The 150+ tanks I have cycled since have all been without fish. I wrote 3 cycling articles, none were about how to cycle with fish. The two fish in articles I wrote were on how to undo the mess of a fishless cycle which has gone off the rails.