I recently set up a temporary fish-only tank with 39 fish around 5cm each in 94L tank. I got a spare external filter and swapped half the ceramic media in it with that from an existing cycled, running tank. Suffice to say it wasn't sufficient as ammonia started building up shortly. I moved over a small internal filter from a different running tank, again this wasn't enough to stem the buildup of ammonia. So I looked at bacteria in a bottle products. Of the ones on the market, Tetra SafeStart is widely said to be one that really works, but also it is one of the more expensive ones. Unfortunately the local store to me only sold the tiny bottles and were near their expiry date so weren't "fresh". Long story short, I found API Pond Starter Pack, which consists of a bottle of Pond Quick Start and Pond Stress Coat. I believe the pond versions are same as the normal versions but more concentrated. Best thing was, this pack was £4 in Pets At Home (in store label was £8, but website and till used £4). Worth it for the dechlorinator alone so effectively I had nothing to lose to try out Quick Start to see if that would give a boost to the filter quickly.
I got home, put in the stated dose and tested the next day. No good. Still got ammonia. After much thinking, I came across API's document where they describe their test "proving" it does work. Looking at it, I found the key difference. My tank was far more heavily stocked than theirs. Logically, I'd need a much bigger dose. No problem, since this was a pond kit, I could easily overdose proportionately in my tank. Partial success, I then saw excess nitrites accumulating. After a day, that was gone. After another day, ammonia dropped back to zero where it has stayed for a day longer, even with feeding. Note during this time I did one water change to lower the nitrites, as well as used calcium chloride to help detoxify it. I also used Interpet ammonia remover initially, then later Seachem Prime to detoxify ammonia buildup.
I couldn't say this proves or disproves the working of Quick Start since I had some cycled media in tank before its introduction. If there's a PAH you can get to easily the pond kit might be a cheap enough way to give it a go.
On a comparison of Quick Start with SafeStart, both use nitrosomonas to deal with the ammonia. They differ in nitrite munchers, with the former using nitrobacter, the latter using nitrosospira and nitrospira.
Now, that aside, the traditional route for fishless and plantless cycling is to add an ammonia source and wait... then test to see the ammonia being consumed, producing nitrite. Wait longer to see nitrite being consumed, and you're done. The API master test kit is popular as one of the best value test kits. About this time others may say test kits are pointless and inaccurate, but we do need to know when the ammonia and nitrite phases have gone, and accuracy isn't important. We just need to know the difference between zero ammonia and nitrite, and high levels of such. Many like to use a pure ammonia source for this, although you can use fish food and let it break down.
Vinkenoog1977, this is the first time I've heard of massive frequent water changes to cycle a tank. Got more on this method, what is the mechanism for it working?