GoGuppy
13th November 2007, 02:39 PM
G'day all
First of all, apologies for the long winded monologue following, but things aren't always straight forward and easily explained. Please bear with me on this one.
As I've mentioned in another post a couple of weeks ago, my filter is working beautifully and I'm measuring nil nitrates in the tank water at present. This is usually considered to be an excellent result and I achieve this with using mainly biological media in the canister.
I'm also pumping CO2 into the heavily planted tank and fertilising with iron (ferreal) on a weekly basis and use Dupla 24 drops about every 2nd day for trace minerals. The lighting level is high and I leave the lights on for about 11 hours a day.
Now I must say, that although I appear to be doing "all the right things" (if there is such a thing :wink: !!) and some of the plants are growing taller and pumping out streams of oxygen bubbles, they don't seem to be growing as luxuriously as when they were newly bought. :(
As a keen gardener (of the home & garden variety) I know that plants need both macro nutrients and micro nutrients. The micro nutrients include iron, molybdenum, zinc and the like and these are provided by the ferreal and dupla drops. The macro nutrients are known as NPK that is nitrogen, phosphate and potassium. The nitrogen and phosphate come from fish waste and plant decay, and the potassium comes from somewhere (just can't think now, it'll come to me).
Now normally, in simple terms that I can understand, a biological filter converts the ammonium from fish waste to nitrites and this is then converted to nitrates, all within the filter medium. Nitrates are less poisonous than nitrites and are kept to a suitably low level by water changes. So far pretty straight forward. So the nitrates (an oxidised form of nitrogen) are absorbed by the plants, the plants get their shot of N and grow healthily, right?
Hang on, that's where I have a problem. I have nil, zilch, zero nitrates in my water, so my plants don't get the macro nutrient nitrogen they need. Why is this so (IF this is so :wacko: )?
The media I have in my filter are mainly sintered glass noodles. I am told these not only provide aerobic (air rich) bacterial action on the medium surface in the flow of oxygen-rich water, but deep within the sintered surface cracks and micro cavities where there is no water flowing past there is anaerobic (air starved) bacterial activity going on. Guess what these anaerobic critters do? They convert the nitrates to nitrogen gas which when it is returned to the tank evaporates out of the water before the plants can get their fangs into it.
So is it possible, that that I need to dose Nitrogen, in a form the plants can readily absorb? Has anyone come across this problem in a planted tank before?
I am aware that Seachem produces a product called Flourish Nitrogen. Has anybody used this to compensate for lack of nitrates in their tank?
Should I remove / reduce the amount of sintered glass media I have in the filter and just use ceramic noodles as a biological medium in stead (ceramic noodles are not sintered, so do not have the micro cracks where the anaerobic bacteria live)?
Cheers
First of all, apologies for the long winded monologue following, but things aren't always straight forward and easily explained. Please bear with me on this one.
As I've mentioned in another post a couple of weeks ago, my filter is working beautifully and I'm measuring nil nitrates in the tank water at present. This is usually considered to be an excellent result and I achieve this with using mainly biological media in the canister.
I'm also pumping CO2 into the heavily planted tank and fertilising with iron (ferreal) on a weekly basis and use Dupla 24 drops about every 2nd day for trace minerals. The lighting level is high and I leave the lights on for about 11 hours a day.
Now I must say, that although I appear to be doing "all the right things" (if there is such a thing :wink: !!) and some of the plants are growing taller and pumping out streams of oxygen bubbles, they don't seem to be growing as luxuriously as when they were newly bought. :(
As a keen gardener (of the home & garden variety) I know that plants need both macro nutrients and micro nutrients. The micro nutrients include iron, molybdenum, zinc and the like and these are provided by the ferreal and dupla drops. The macro nutrients are known as NPK that is nitrogen, phosphate and potassium. The nitrogen and phosphate come from fish waste and plant decay, and the potassium comes from somewhere (just can't think now, it'll come to me).
Now normally, in simple terms that I can understand, a biological filter converts the ammonium from fish waste to nitrites and this is then converted to nitrates, all within the filter medium. Nitrates are less poisonous than nitrites and are kept to a suitably low level by water changes. So far pretty straight forward. So the nitrates (an oxidised form of nitrogen) are absorbed by the plants, the plants get their shot of N and grow healthily, right?
Hang on, that's where I have a problem. I have nil, zilch, zero nitrates in my water, so my plants don't get the macro nutrient nitrogen they need. Why is this so (IF this is so :wacko: )?
The media I have in my filter are mainly sintered glass noodles. I am told these not only provide aerobic (air rich) bacterial action on the medium surface in the flow of oxygen-rich water, but deep within the sintered surface cracks and micro cavities where there is no water flowing past there is anaerobic (air starved) bacterial activity going on. Guess what these anaerobic critters do? They convert the nitrates to nitrogen gas which when it is returned to the tank evaporates out of the water before the plants can get their fangs into it.
So is it possible, that that I need to dose Nitrogen, in a form the plants can readily absorb? Has anyone come across this problem in a planted tank before?
I am aware that Seachem produces a product called Flourish Nitrogen. Has anybody used this to compensate for lack of nitrates in their tank?
Should I remove / reduce the amount of sintered glass media I have in the filter and just use ceramic noodles as a biological medium in stead (ceramic noodles are not sintered, so do not have the micro cracks where the anaerobic bacteria live)?
Cheers