Fishless cycle going funny

[blue_soda025]

I've been doing the fishless cycle in my 20 gallon for 20 days. The ammonia has spiked and it seems nitrites have finally reached zero about 2 days ago. However, ammonia was still at about 0.5 ppm yesterday and this morning. It looks like the cycle has stalled.. or something. Before, it would drop slowly (took about 3 days for 2.5 ppm to drop to 0.25 ppm), but now it's not dropping at all?! I was under the impression that the cycle is done once nitrites drop to zero. Also, the pH is quite low; about 6.2 or lower (test kit doesn't measure lower than that). Could that be affecting the bacteria that process the ammonia? I haven't tested the kH, but I know our tap water is soft. The nitrates have been dropping rapidly as well. It was > 110 ppm before. Now it is only around 10 ppm or so. I only have two live plants in the tank right now; an amazon sword and elodea. The elodea seems to be growing rapidly, but it seems odd that it would affect the nitrates that much. Any idea as to why the ammonia wouldn't be going anywhere (or if it is, very slowly)?

 

[bigscout]

2 issues, both of which you have mentioned.
1st, The bacteria require carbonate, to function, and use it up at a pretty high rate during a fishless cycle. So if your pH is that low, it's likely your KH is gone and your cycle would in fact stall.

next is the plants. Ammonia is the prefferred nitrogen source for plants so they will use it up when growing rapidly, and elodea is one of the big time nutrient hogs out there. Plants are also a very dangerous idea with high ammonia titers since high ammonia tends to breed algae very well. by having plants in a fihless cycle, you requiore yourself to ahve light and that is a situation ripe for algae growth. it will appear overnight almost if you continue.

Bring up your Kh, and figure out how to deal with the plants. Here is a great article that covers just about any questions or details you could have, including those I already touched on.

Cycling a tank

 

[blue_soda025]

I have tested the kH of the tap water and it came out as 1 dkH. What's a good way of bringing it up? I was thinking of adding baking soda for instant results, but surely there's a better way for the long term.
In this case, would it help to do water changes?