I hit up a bunch of forums. General consensus says the rock is in no way bad for the tank. Just not good enough for buffering your tank for filtration. You have visual porosity (holes on the rock). Then there is internal porosity (the core). Surface porosity (the actually surface of the rock). I am guessing it is the internal porosity that is problem due to it's lack of ability to absorb water. This is where your anaerobic bacteria is that completes the nitrogen cycle process that brakes down everything into a gas that dissipates out and off your live rock up to the top of your tank releasing the nitrogen in to the air. Limestone from what people are saying is good for a large tank's base rock for 200-1000g. You put a little bit of the limestone on the bottom for a base to save a little bit of money. Then add your expensive rock with high porosity best for filtration on top, because it is expensive. Where in a biocube of 29g. You basically need all the help you can get. I know you don't want to pull the rocks, but you are short changing the nitrogen cycle and doing 3/4 of it and leaving out the most important part of it. This is where your nitrate problem is. Your nitrates are not turning into the gas final stage to leave your tank. If you like your aqua scape. Then get either a chunk on that marine pure rock and stuff that in where your bioballs used to be. Chemicals are your quick fix and it is not working. I am a firm believer of the natural way and getting your tank to run like a well oiled machine. This is just my take on it and how I would address the issue to stop future headaches. Purugin also. Not to tightly packed in a bag so it has some kind of tumble. Good luck with it man. I hate headaches. At least you don't have some major expensive stuff in there. Also on a side note. To put it into more perspective. If you have say 14lbs of a rock with less porosity vs 14 lbs Fiji. You would need about 100lbs of the rock with less porosity to do the work of a 14lbs of Fiji. Plus the 14lbs of rock with less porosity would be smaller than 14lbs of Fiji. So you actually are short changing yourself in surface area. So it would be about 2-3lbs of Fiji in a 29g. That is not enough flirtation even for hermit crabs. The numbers are not right, just put in a general perspective. Hope this helps and you get a fix to your issue. Take care.
