Actually, you may need to do water changes, it depends on your levels. But there is a bigger issue here which I will explain. As you know once the ammonia converting bacteria begin to colonize, they turn the ammonia into nitrite. So here is why and where you need to be on top of things.
You should not allow your ammonia level to get much above 5 ppm on an API (or similar) test kit. At 6.4 ppm the ammonia is too much and can damage the bacteria and you must change water to get the level down. This is the only way you can have any control over ammonia levels.
The problem is that ammonia turns to nitrite and this can also impede a cycle and kill bacteria if it gete above 16 ppm on and API (or similar) test kit. The problem here is that the API kit stops well short of that level at its max. of 5 ppm. So if you have to do a water change for ammonia levels you may also have to do them for nitrite as well. However, you will have no idea when this might be required using such a test kit. You will have to do diluted tests any time your nirtite reading hits the top level on the chart.
You will need to do diluted testing. You will have to do diluted tests any time your nirtite reading hits the top level on the chart. This requires you get a bottle of distilled water, a clean measuring cup and a clean glass. You want to dilute larger size sample to mimimize testing/measuring errors.
1. Add tank water to fill the measuing cup 1/2 way, then fill it the rest of the way with distilled water. Then pour from the measuring cup into the test vila and do the normal test. Multiply this result by 2 to know your real nitrite level. Of course if the diluted test reads at the top of the scale you will have to dilute further and retest.
2. Pour the sample in the measuring cup into the clean glass an then put back enough into the measuring cup to fill it 1/2 again. This time add enough distilled water to get to 3/4 of a cup. Use this to fill the test vial and test again. This time multiply the result by 3. If your reading is still at the top of the scale do not bother to test any more,do a 50% water change.
3. After the water change do the regular nitrite test again without diluting. If the level is at the top, repeat the 50/50 diluted test as above. If the result is still at the max level d another 505 water change
The goal here is to get the nitrite level down to no more than about 10 ppm. A bit under is fine, above is not. You need to leave some room above 10 for the nitrite to rise before having to change water again.
Using shrimp works to cycle but it gives you no control over how much ammonia is produced when. In a normal fishless cycle we use the ability to control ammonia levels to insure neither they nor nitrite levels ever go too high. Here you must be more alert and do a bit more work to keep things under control.
