All depends on how "good" your seed material was, and by good I mean how much bacteria was on the substrate. I fishless cycled in 17 days or so with a small bag of gravel so its definitely possible to do it pretty quickly. You have fish so you
CANNOT do some of the steps (raise the temp way up, etc).
Your stocking is very light for your size tank which is a plus. If your seed material is in fact viable (ie has active living bacteria on it), it shouldn't take long for the biofilter to catch up. If you had a goldfish/pleco/adult fish it could definitely be a long painful process.
Please note it should be near impossible for your ammonia level to be below 1ppm. Since that is what your tap has you can never get below 1ppm when doing water changes (until the bacteria have multiplied to the point where they are converting more ammonia than is being produced). If you're reading under 1ppm either you have more bacteria than you think (good thing
), or your test is not accurate (I don't know if your dechlor product affects the test).
I would recommend for your sanity and the fish's health to try to get more seed material. Keep up the water changes. For ease of use 50% PWC's are much more beneficial than 25% PWC's since you effectively cut the concentrations of toxins in half (and the extra work is minimal, trust me I do 50% PWC's on my 20gallon planted tank and 10 gallon QT tank every week, by hand, with a bucket
). A 25% PWC really doesn't do much in the grand scheme of things with ever rising levels. A 75% is ideal but you need to be careful about stressing the fish and making sure the temp of the water you are adding back in is EXACT.
And I would like to commend you on your proper treatment of the fish under these circumstances. Many people in your situation get lazy and let the levels get higher then they should, or just ride out the cycle and get new fish after the tank has stabilized. You're doing a great job!
Keep squishing that bag!