I do not think you are not following the cycling directions here as nowhere in those directions does the word top up ever appear. To cycle a tank the total number of ammonia doses needed, including the 1 ppm snack dose, is normally 5 or 6. There is no topping up, there is only adding the amount needrd to produce 3 ppm for your volume of water plus a 1/3 amount for a single snack.
The most common cause of stalling a cycle is to high a level of nitrite. this is caused by dosing to much ammonia and dosing it too often, This pushed nitrite to a level where they stall a cycle and may even kill of the bacteria. On an API kits this level is just over 16 ppm. But the test only goes up to 5 ppm. Because of this one has two choices, either learn how to perform diluted testing or else follow the directions exactly as layed out in the article you thought your were following.
The amount and frequency of the ammonia additions in the cycling article here were calculated specifically to avoid the need for doing diluted testing but also because when they are followed it is impossible to create too much nitrite. The only way those directions can fail is when they are not followed and new hobbyists decide to make it up as they go along for some reason.
Dosing too much ammonia and what comes with it cause one's pH to fall or crash.
y suggestion you you is to do enough water changes to bring your ntirite reading to under 5 ppm. When you have done this then follow these directions. Do not think about them, do not alter them, just follow them as if you were a robot
-After you do the water changes your ammonia should be 0 and your nitrite under 5. Add 3 ppm of ammonia and begin testing every other day for ammonia and nitrite.
-After the ammonia addition, while waiting for nitrite to rise, peak and drop, the bacteria will need a maintenance feeding. When you get two consecutive ammonia readings of 0 ppm, give the bacteria a “snack” by adding 1/3 of the full amount. This “snack” should be needed somewhere between days 21 and 27 of the cycle. The snack should not be given until at least 4 days after your wc and 3 ppm addition. Add 3 ppm, test in 2 days, test again in another two days. if both reading for ammonia were 0, then give the 1/3 amount.
-After the maintenance feeding, whenever you test and ammonia is .25 ppm or lower and nitrite is clearly under 1 ppm, it is time to add a full ammonia dose again and test in 24 hours.
If ammonia and nitrite both read 0 ppm, you are cycled. Do a large water change, be sure the water is the proper temperature, and add fish. The odds are this will not be the case quite this soon.
When adding ammonia use the ammonia calculator. Set it for 3 ppm and for 85% of the advertised tank volume. The calculator shlould be more reliable for hitting 3 ppm than adding and trying to test, so please do not try that.
Good luck and report back how things are going
-If ammonia and nitrite do not both read zero, continue to test daily. Whenever ammonia is again at .25 ppm or less and nitrite is clearly under 1 ppm, add the full amount of ammonia and test in 24 hours. Follow this pattern of testing and adding until both tests read 0 ppm. The cycle should not take much longer to be completed.
