Hypothetically speaking ....

[Scuba Guy]

If our plants in our tanks using light and injected CO2 take up all of the Nitrate possible in order to grow (my tank has gone to zero Nitrate - in fact I may have to add some)....then hypothetically speaking, does cutting the light and eliminating the CO2 cause the plants to release nitrates back into the tank in a reverse mechanism?

In other words, if I were to let my plants DIE without taking them out of the tank first - they could (correct?) kill my fish with a sharp increase in Nitrate.

Does this make sense?

[jeffs99dime]

If our plants in our tanks using light and injected CO2 take up all of the Nitrate possible in order to grow (my tank has gone to zero Nitrate - in fact I may have to add some)....then hypothetically speaking, does cutting the light and eliminating the CO2 cause the plants to release nitrates back into the tank in a reverse mechanism?

In other words, if I were to let my plants DIE without taking them out of the tank first - they could (correct?) kill my fish with a sharp increase in Nitrate.

Does this make sense?

that's a very good question. i would have to say yes to that. although, i've never tried it and wouldn't ever try it lol. i'm going to try and find out. i'm very interested. good one!

[Scuba Guy]

I am not going to try it either - but it seems reasoable that when plants start dying and we do nothing about it, that's worse for the aquarium than if we had never put plants in the first place.

Plants are better for the aquarium over all, but are a responsibility. Ignore them and your fish suffer.

At least that's what I am beginning to internalize.

I have had fish and plants on and off for a lot of years. And only now am I paying attention.

With plants (lots of em) - you don't have to change the water as much....but if you don't change the water, then your fish will stunt if they are not already full grown. (fish hormones in the water do that I have learned).
Let the plants die, and your screwed.

(I'd love to test this some day - not the fish dying part - but the Nitrate increase)

[Chrona]

Well, as far as I know (and I may be wrong), the nitrates taken in by the plant are converted into plant tissue and energy that have different chemical compositions (chlorophyl, ATP, etc). I'm sure that it would eventually decompose into some kind of nitrogenous waste, but probably not before going through some slow intermediate steps.

When I first started keeping plants, I had a bunch die and they just made my water cloudy. I didn't really notice any change in water parameters. But then again, this may just be due to the fact that plant matter breaks down slowly (compared to fish waste) and that I was doing water changes every 5 days or so.

[Chrona]

found some info on this.

http://www.indiana.edu/~bradwood/eagles/nitrates.htm

I guess I just didn't have as much decaying plant matter as I thought (or the other plants were absorbing the ammonia), because this says the bacteria that breaks down the proteins in plant matter gives off ammonia (!), which is then eventually broken down into nitrates through the nitrifying cycle. So yes, a large amount of decaying plant matter will:
1) suck alot of oxygen out of the water
2) give you an ammonia/nitrite spike
3) raise nitrate levels eventually

[jeffs99dime]

found some info on this.

http://www.indiana.edu/~bradwood/eagles/nitrates.htm

I guess I just didn't have as much decaying plant matter as I thought (or the other plants were absorbing the ammonia), because this says the bacteria that breaks down the proteins in plant matter gives off ammonia (!), which is then eventually broken down into nitrates through the nitrifying cycle. So yes, a large amount of decaying plant matter will:
1) suck alot of oxygen out of the water
2) give you an ammonia/nitrite spike
3) raise nitrate levels eventually

this is true, but you nitrate levels will rise over time without w.c. even if you don't have live plants. just throwing that in there also.