Nitrate level and Excel dosing - observation
This is just an observation about my use of Flourish Excel and nitrate levels in a heavily planted 55 gallon.
I stopped using Excel in my 55g for a couple of weeks as an experiment. Interestingly, my nitrate level went up to 30ppm and stayed there. A few days after I started dosing Excel again, daily and not exceeding the recommended rate (I don't do the water change "overdose" Excel recommends), my nitrates dropped back to zero. As per Excel's promise, my plant growth picked up noticeably also. In my system, Flourish Excel doubles or triples my plant growth rate comparing plants from my quarantine tank (no excel) to those in my 55 gallon.
I assume the increased plant growth, due to Excel dosing, uses up the nitrate in the water column really quickly. Not an earth-shattering observation about the nitrate level, but I found it interesting.
This is as you say what one would expect, though I would venture that it is not the nitrates but ammonia that is the reason.
Aquatic plants prefer ammonium over nitrates as their source of nitrogen, and are very fast at grabbing ammonium (ammonia). The Nitrosomonas bacteria are very much slower, so all else being equal, plants will use more of the ammonia and faster. Nitrifying bacteria in a well planted tank is much, much lower in numbers than it would be without plants, all else being equal.
CO2 is often the nutrient in least supply, which is why the lighting has to be minimal and in balance. There are probably more of the other essential nutrients available, so once you increase carbon (via Excel in this case) the plants can increase their photosynthesis level accordingly, up to the point where something else is the limiting factor.
Without additional carbon (via Excel) the plants will photosynthesize up to the limiting factor, probably carbon, and ammonia beyond this will be more likely to be taken up by bacteria. Plants can also take up ammonia as a toxin, but at this point the bacteria is on more of an even ground. The increase in bacteria means of course an increase in nitrite, so Nitrospira increase to handle that, producing more nitrates.
In natural (low-tech) planted tanks nitrates should be below 10ppm, down to zero. This state indicates the plants are utilizing the ammonia well, and the system is balanced. An increase in nitrates would suggest that the balance is out.
Plants find using nitrates to be "extra work" since they must convert it back into ammonium. They will do this if ammonium is no available, and assuming other essentials are.
Great information, as usual, Byron!
My suspicion is the nitrates elevated (without the Excel) due to chronic overfeeding. I know I do it, but it's a very hard habit to break! I'm still trying to watch the overfeeding, since Excel not a substitute for proper feeding levels.
Thanks for the information guys. This may explain why I've seen nitrate levels increase in one of my tanks - a tank I used to dose with Excel but then stopped. I think I'll resume the Excel for a few weeks and see if it affects the nitrate level.
However, the tank in question has slightly elevated nitrate levels, in the 40 range. The fish are healthy and active, and I perform 20% water changes in that tank 3 times a week. I don't think I'm in the danger zone, but it makes me a bit uncomfortable. I'm a just a little curious to see if the nitrates drop at all if I resume the Excel for a while. It's amazing how many conflicting opinions there seem to be on Excel, and what it really does or doesn't do.
Again, thanks for the feedback. I value your opinion.
Nitrate in a planted tank should be below 10ppm, mine run at 5ppm in the heavily-stocked tanks and near zero in the others. I do not dose any form of carbon, so this is just natural in fairly heavily planted tanks. I would look into why your nitrate is higher and solve the issue. If the fish load is balanced for the tank volume and plants, nitrates will guaranteed be very low. Couple of ideas.
Have you tested your tap water on its own? If there are nitrates in this, that can be dealt with. If you haven't, test it for ammonia, nitrite and nitrate.
If you are using the API liquid test kit, you need to shake Regent #2 in the nitrate test for 2 minutes, not just 30 seconds as in the instructions; otherwise you may well get a faulty (and much higher) reading.
Even though I use Excel, I agree with Byron regarding the long-term potential harm. I am much less enthused about Excel than I was 3 months ago. I love the accelerated plant growth, but...
The active ingredient in Excel, at a much higher concentration than found in Excel, is known to cause human lung problems. I make a special effort to not inhale the fumes when using Excel. Prevention is easy...
Once I can afford it, I'm going to try (modest) pressurized CO2 instead. Don't want to harm my fish using that either! Plants will grow without either Excel or added CO2, but I'm just impatient!
--I need to shake my API reagent longer also...
I generally shake the regent #2 for about a minute. I'll try 2 minutes and see what happens. Possibly my readings aren't as high as I think. Also interpreting the color chart can be a bit subjective. Sometimes I'll ask my wife what she thinks, and we'll disagree. I've never tested my tap water - I'll test it later today and see what it registers.
Okay, just completed fish tank maintenance day, including running all the water tests. First, nitrates coming out of the tap register 5 ppm. As far as the tank in question, after shaking the #2 bottle like crazy for a couple of minutes, I'm calling the results 20 ppm. Shaking the regent longer did make a difference.
For the record, the other readings from the tank were ammonia at 0, nitrites at 0 and pH around 8.0. All these readings have been trending the same for the last year. We have high pH water coming from the tap, and I take that into consideration when stocking.
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