[Straight shooter]

I'm after some theories..

I just rescaped and disturbed aquasoil quite a bit, leaving the water quite dirty. The soil is ~2 years old. I did a 90% WC change following the rescape, then refilled with treated tap water to reduce the turbidity. The tank is heavily planted. I dosed K and micros following the water change.

Would it now be necessary to fertilize with nitrate and phosphate, or would disturbing the aquasoil leave enough N+P in the water column?

 

[greaser84]

I would say yes. Even if you kicked up nutrients from the substrate you did a 90% water change probably removing the majority of nutrients from the water column. Testing would give u a definite answer either way dosing won't hurt anything.

 

[Straight shooter]

Thanks greaser. Just tested nitrate using an API test kit. Result was 10ppm nitrate 24 hours after a 90% WC. I didn't add any additional N+P after the WC, only K and micros. Before the water change, and before the soil was disturbed, my nitrate was around 5ppm. So that gives a good idea of nitrate accumulation following heavy disturbance of the soil and a 90% WC. When I say heavy disturbance I mean 50% of plant species in a heavily planted tank were uprooted, mainly stem plants. The water was completely brown and nothing was visible through it.

I don't have a phosphate test kit.

My theory is that lots of nitrate is released into the water column following heavy soil disturbance, and that a large water change is necessary following this. My tank is medium light CO2 injected and 10ppm nitrate is about right for my plants, therefore no further water change is needed. If I was running a low tech I'd do another 50% WC to get that down to <5ppm nitrate.