Have your nutrients ever become "self-sustaining"? - The Planted Tank Forum
 
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post #1 of 10 (permalink) Old 06-25-2005, 02:30 AM Thread Starter
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Have your nutrients ever become "self-sustaining"?

Is it common -- or, has anyone else's tank -- ever reached a "sweet spot" in terms of ferts, where the nutrients are sort of self sustaining?

For the past several months, I have been dosing EI style with Greg Watson ferts: macros some days, micros on the alternates. I end the week with a 50% water change. Well, last week, I did my usual water change and, after filling, decided to test the water (which I hadn't done in a while), to see what my fert levels were. Even after the water change, I had a solid 10-13ppm reading of NO3 using my Lamotte test kit. And, with my Red Sea kit, tested 2+ppm of PO4. These are the levels I usually try to keep in my tank, but I was surprised the macros were registering so high, even after a water change. So, I decided to withold macro ferts that day and retest in a couple of days. I tested a couple days later and the levels were still holding.

It's kind of nice to see the ecosystem sustaining itself. I suspect my recent addition of some larger rainbows, plus an increase in frequency of feeding (along with some occasional pre-washed frozen food) are the primary reasons for the macros holding strong. Likewise, I have swapped out some of my hungrier plants and only run my 192w for 6 hours, as opposed to the whole 11 hour photoperiod ( I run 96w CF for the whole 11 hours).

I am continuing to supply micros. And I will monitor my tank to see if the ferts continue to sustain themselves after the next water change or bottom out. While I know it's better to have more nutrients than too few, and I could probably continue dosing macros regardless, I'd rather not overdo the nutrients if I don't have to -- as that can sometimes cause problems, too.

Anyone with similar experiences?
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post #2 of 10 (permalink) Old 06-25-2005, 04:56 AM
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Could be the test kits are going bad too. I have thought I had a similar thing happen in the past. Every time it was a wonky test kit.
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post #3 of 10 (permalink) Old 06-25-2005, 08:22 AM
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Organic waste from fish can throw off test kits, that's a lesson I have learned with my heavy load tank. So I keep dosing EI amounts and doing water changes, regardless what's coming out of fish.


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post #4 of 10 (permalink) Old 06-25-2005, 10:16 AM
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Test kits ? Thats the true beauty of EI... no test kits required. (except in beginning)

Dose , wc , dose , wc .... I agree though... dont trust the kit with a constant reading.
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post #5 of 10 (permalink) Old 06-25-2005, 04:09 PM
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Quote:
Originally Posted by shalu
Organic waste from fish can throw off test kits, that's a lesson I have learned with my heavy load tank. So I keep dosing EI amounts and doing water changes, regardless what's coming out of fish.
i understand this but...do plants not use the organic wastes from fish etc. as nutrients?? if your levels are naturally moderate to high and you continue to add NO3 and PO4 won't those numbers be WAY high??
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post #6 of 10 (permalink) Old 06-25-2005, 07:09 PM Thread Starter
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fishyface

I'm a little confused, too. How is the nitrate from supplied doses of KNO3 any different or better for the plants than naturally occuring nitrates in the water from fish food and fish waste? I can't imagine it is. Test kits, I don't believe, are selective as to which nitrate it is registering -- the kit measures the total nitrate in the water (nitrate from food, nitrate from fish waste, nitrate from Greg Watson KNO3). Someone please do correct me if I'm wrong. I'm probably simplifying things.

As for the test kits going bad, I did "control" test them against my tap water and a few controlled nitrate dosed water samples of varying amounts. Everything seems to be in check, especially the Lamotte kit.

When I first set up my tank months ago, I did the occassional water test, more out of curiosity to see how the system was working and what my plants were consuming. I had less fish in my tank then, lots of stem plants, 192w on for 11 hours, and tons of Water Sprite. Using my Lamotte kit, it was amazing to see just how much NO3 the plants would suck up in just 2 days. They consumed nearly all of it. I dosed "blindly" from that point on: no testing, just EI dosing and a water change.

So why did I decide to test recently? I cut down my wattage. I added a lot more fish. I fed a lot more. I removed all of my Water Sprite and nearly all of my stems. My CO2 was still strong but I seemed to be getting faster dust algae on the glass and more spot algae. Decided it was time to test the water. That's when I saw high NO3 and PO4, even after water change.

15ppm of NO3 and 2+ppm of PO4 is enough for my tank. No need to go higher. And since backing off supplemental macros, I've had less dust algae on the glass and less spot algae. For my tank, those levels seem like the sweet spot. I tested again today -- if anything, my NO3 went up a point. Water change time tomorrow. I will check again next week. If my fish, feeding, plants, and light stay constant I will only dose micros for a while and see what happens.

Yes, the beauty of EI is not testing. I like that. So hey, if I don't have to dose water column macros either, even better.
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post #7 of 10 (permalink) Old 06-26-2005, 01:02 AM
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Any time you change conditions drastically in a tank you will of course need to test, removing plant mass, removing watts , adding fish etc. add up to big changes in nutrient demand.
NO3 is the hardest to track since cleaning habits of the tank and filters can really effect the levels. Filter media/pads are notorious for NO3 supplement just because of the waste they take care of in uneaten food , mulm and any plant decay.

If you know your kits are good then roll with it and enjoy not having to dose as often .
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post #8 of 10 (permalink) Old 06-26-2005, 01:52 AM Thread Starter
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Hey Buck

Good follow up. I just cleaned my filter today after the usual month. Perhaps that was sustaining the NO3 as well. I'll check again in a couple of days.
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post #9 of 10 (permalink) Old 06-26-2005, 02:51 AM
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Tanks with lots of fish usually don't need dosing of any nitrate or phosphate. The fish waste will break down into nitrate, and the phosphate is supplied from the fish food.

Nitrate is not the best nitrogen source for plants. Ammonium (NH4+) is much closer in structure to an amine group (NH2) which is used to make plant proteins than Nitrate (NO3). Because of that plants are able to utilize ammonia and ammonium more easily than NO3. It's therefore more beneficial to simply increase the fish stock and feeding level in the tank instead of dosing nitrates/phosphates.
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post #10 of 10 (permalink) Old 06-26-2005, 08:30 AM
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Plants will store up nutrients way beyond their needs, luxury uptake.
If you have been dosing fat levels as I suggest often, then switch to lean or no dosing for a few days, you will not see much change.

Wait a week or two for some macros.
You should see the PO4 removed first them the NO3 uptake slow.

I test tanks without fish or critter loads to remove any external things besides the plants and inorganic ferts.

This makes thing simpler.
Adding fish = more nutrients, some organic fractions etc. But more is fine.

Give the testing a longer run(3 weeks is a good general time frame) and test daily and write the ppm down. Calibrate the test kits againt a known standard solution also.

Check you food sources and volumes.
Also, what is the light intensity?

Less light can easily have most of the % of the macros from the fish waste.
Non CO2 tanks can have all of it from the fish waste for 6-12 months without issue or longer.

Higher light, less fish=> more inorganic dosing will be required.

You can target less macro dosing from the sounds of things, say 1/2 of what you were dosing.

More will not hurt, but less will not either in your specific case.

the 10-13ppm of NO3 after a water change is about right.
If you dose 10-20ppm per week of NO3, then that is about what you want as a minimum NO3 level(about a 3-5 days supply).

Test kits get squirrley in the lower end of the testing range.
This is true for all of them.

They make specific LR and MR and HR test kits for research but not for the hobby really except the higher end Lamotte and Hach type test kits.

Rather than approaching this from a test kit only method, consider dosing liquid solutions for more precise dosing.
While more control is not needed for good horticulture, this will give you more precision in dosing EI.

You can test and individualize any tank using the plants as the "test kit".
Run the test 3 weeks and vary one parameter each 3 week block and go down till you see a negative plant respose, then bump it up to ther next higher dosing rate.

Ina about 12-16 weeks , you will know most of the plant's response's to dosing limiting nutrients for each nutrient.

Again, no test kit needed, but you can use a test kit for confirmation provided the test kit is calibrated and consistent.

I do this when I want to test something. I also have a few thousand dollar's worth of test equipment.

I do EI for plain old horticulture.

Regards,
Tom Barr



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