Originally Posted by xfatdannx
I'm still fairly new to the aquarium hobby, are there specific "nutrients" you are referring to, just nitrates?
Not just nitrates. Plant life uses nitrogen, phosphates, potassium, several others, plus light and carbon. And produce plant tissure and oxygen.
But not every plant has to use ammonia/nitrates for nitrogen. Some plants be it soybeans in a farmer's field or cyano in our tanks can take nitrogen from nitrogen gas instead.
Plus plants consume ammonia/nitrates but also other things like low oxygen bacteria. The bacteria actually "reverse" got forward aerobic bacteria cycle and reduce nitrates to nitrItes and then to nitrogen gas. So at the surface of the substrate you can have a low oxygen, high co2 environment which is returning nitrogen gas.
So IMHO what can happen is you go for several months. Things are doing great. Tanks look great. Plants thriving. Then one day you notice a little slime (blue/green Fw, red marine) on the substrate/rocks. Then that initial slime gets bigger and bigger and in a very short while everything in the tank is covered.
What happened? Nitrates went to unmeasureable values because bacteria as well as plants consumed the nitrates. So the cyano started consuming the nitrogen gas and phosphates and rapidily bloomed.
Meanwhile the ammonia/nitrate plant life had less phosphates available so started being starved.
As a result the tank rapidily is becomming cyano dominated vrs plant dominated.
If you kill the lights and stop adding food, the cyano will die off faster then the plant life. Plus the less food reduces phosphates as well as generally reducing the bio load. So the cyano dies off and returns the nutrients (including the nitrogen gas-nitrogen) to the aerobic bacteria cycle and the plant life.
So you rebalance the tank in favor of the plant life at the expense of the cyano.
Then you adjust lighting and feeding so the plants remain in control and the cyano is held at bay.
At that point you still cyano just not huge noticable levels. What in fact may be happening is cyano is returning nitrogen to the plants just like farmers rotate crops to return nitrogen in fields.