[Krav]

A few years ago, a filter went out on a 29 gallon tank. I was away at work, so I came home to dead colony of Neoloamprologus pulcher. I was so upset that I just drained the water, disposed of the fish, and left it sitting there.

Last month, I decided to get it started up again. Replaced the sand, replaced the filter, rinsed the rocks, hosed down the tank and wiped it down.

I attempted to fishless cycle with the shrimp in a media bag and wringing out a filter sponge from another tank. Current water parameters: 0 ammonia 0 nitrite and 160 ppm nitrate. This has never happened before, and I can't figure out what caused that much nitrate. I did one 25% water change in week 2.

Do I need to empty out all of the water, rinse the filter media, and start all over again? And what could have possibly caused this much nitrate? Did I possibly not clean the rocks off enough?

 

[Krav]

Do you have any nitrate in your tap water? If not it has to be from something inside the tank or it's accessories that retained some pollutants.

During the month, did you have the usual ammonia spike, then nitrite spike? A lot of nitrate can be created just from the cycle.

Tap water read zero for everything. During the first week, there were normal ammonia readings, no nitrites, and already had nitrates in the water. I just assumed that there was some nitrate that was rung out from the filter sponge from the other aquarium. Second week there was still ammonia, some nitrites, and 40 ppm of nitrates already. This prompted the water change. By week three, the ammonia was nearly gone, there was the usual nitrite spike, but nitrates were already at 100 ppm.

The only thing that I can think of is that the rock seems to be fairly porous. Almost like lava rock. I'm wondering if the rock had nitrates that didn't completely rinse out, but leeched into the aquarium water when it was sitting completely submerged.

I will probably try an almost full water change and see what happens. I'm going to move the rock into a little 10 gallon quarantine tank since its currently empty and do before and after readings to test the rock theory. I wouldn't think that one small prawn could result in that much nitrate after a cycle, but I could be mistaken.