dwarfgourami
Fish Connoisseur
This filter will be to small for the dimensions of the tank you mentioned, which should work out as 96 ltrs=25 US gallons. Fluval do more powerful filters that should be the right size.
Also, as the tank is quite short, cycling with danios, though possible, is really not ideal. Can I plug for fishless cycling? Although the post you got on it sounded very technical, it really isn't that difficult. And I have found it A LOT quicker than cycling with fish on the two occasions that I have tried it.
For fishless cycling you substitute the hardy fish by adding a measured amount of liquid ammonia (from the hardware store) every day (or whenever the readings go down to 0- there are two methods). You use a test kit to see that you add enough to bring the readings up to 4-5 ppm and then add the same amount either every day or when it's gone down to 0 (you test again every 24 hours, before adding more). After a while you will see that the ammonia readings go down to 0 within 24 hours, but the nitrites shoot up high. At this stage you can halve the amount you put in. Once the nitrites also go down to 0 within 24 hours, and the nitrates shoot up, your tank is cycled. At this stage you do a big water change (70%) and then you can add your fish (should be added within 24 hours of big water change, if you can't get to shops, hold off water change and keep adding ammonia as usual).
I would not fiddle with the ph at this time; unless you have absolutely extreme water, it should be fine. I had a ph of 8.4 and both my tanks still cycled within a fortnight.
The big advantage of the fishless cycle is that you are not exposing your fish to toxins. Danios may be hardy, but even they are a lot better off not in a non-toxic environment. And once you've cycled with danios, you are stuck with them, they need a lot of swimming space (really more than 60 cms IMO) and you have to keep a school of at least 6-8; taking up about half of the stocking of the tank you mentioned. Which may be fine if that is what you want, but not everybody does.
The other cycling fish often mentioned is the platy. IME platies are not always as hardy as is thought; they can be prone to bacterial infections if conditions are not right. And they are lovely fish that deserve to be treated carefully.
If the thought of testing puts you off- well, it's not really that hard, and it's something you're going to need to be doing if you cycle with fish too.
To sum up, cycling is not something you can get out of, it is a process that happens automatically when fish are added to water. The fishkeeper's job is to make sure it happens as painlessly as possible.
