Honestly these aren't very good filters. You can get them with bio-wheels, and I'm not sure how well they work compared to the more trustworthy brands, but the ones such as what you bought don't add an optimal amount of oxygen to the filter media in order to establish a bacterial colony. Bacteria grow slowly or not at all with low oxygen.
Here are some other reasons your cycle may have taken so long:
1. Large water changes. They can stress the bacteria and remove a large amount of ammonia which is necessary for establishing a colony. This is why a fishless cycle is better, you don't have to do large water changes for fear your fish may die. Cycling with fish usually only calls for 15-20% water changes every other day. You were worried about them getting stressed which made you decide to do larger changes and prolonged the process.
2. Ph - A bacterial colony takes longer to establish in very high or very low PH. If PH is too low they won't grow at all.
3. Other aspects of your water chemistry could also be to blame. Water chemistry is different everywhere and bacterial growth is effected by many factors.
I think the main thing though is the fact that your bio-filter isn't very good and you were doing large water changes every day.
In regards to Bio-spira, it depends on a lot on how old the bottle you end up with is and how well it was stored. They don't print an expiration date on the bottle so most of, if not all, of the bacteria could be dead. Also, it is supposed to be kept refrigerated, but may have been stored inadequately at one point.
with fish (3 zebra danios, 3 platys) and it took from Labor Day to Christmas. In fact in mid-December I started a thread similar to this one because my ammonia seemed stuck at .25 with no nitrite and 5.0 nitrate. However, by Christmas the ammonia went to 0, nitrite went to 0, and nitrate went to 10. We've been rock solid since then. It sounds like you already bought the bio spira, but I'm guessing with a little more patience you'd be cycled soon.
