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Running a low N/P tank

2048 Views 7 Replies 5 Participants Last post by  Jeff Kropp
I'm not sure if that has been discussed before here but lately as a result of some threads on APC I started to think more and more about running a "lean" system.

My first CO2-fed planted tank had no fish and it ran completely void of algae from the get go. In that tank I tried careful dosing of N, P, and Fe/Traces but at levels that were barely readable on the test kits - N=1 and P of 0.1 or so, few drops of Fe/Traces every other day. That tank would be a typical example of a very lean system - it had 100% Fluorite and I vacuumed it every week.

Later I started dosing my tanks heavier and some did great and some had problems. The common things for all of them was that I had to keep up with the fertilization and water changes or else.

Of course I'm not saying that there is one and best way to run a planted tank.

Because of some discussons here on APC as well as observing the consistent success of some aquascapers lately I started thinking that in the quest for a sparkling clean, stable systema a few things really make sense:

1. Rich substrate
Either prepared, commercial, or just mulm gathered over the months.

2. Extremely clean water
That means not only removal of small floating particles using UV and/or a micron filter. It means water that has not accumulated unnecessary elements or molecules. I find the 3 responses to my question in this topic to be of great value:

4. Steady but limited supply of nutrients in the water column
Both from fish and careful daily dosing. N and P may not even be necessary if the fish load is adequate.

5. Consistent care of the tank
Water changes, fertilizing, feeding, prunning, and so on.

6. Light
Consistent photoperiod of course. But also - a lean stable system would allow increasing the wpg to very high levels or take it as low as you wish. To me personally a brightly lit tank is something extremely attractive.

A good example of a system lean on N and P would be this tank:
If Luis runs that tank the way he runs his other tanks then that is an example of the 6 things I noted above.
And here is something truly amazing to me; Typically Luis uses a lot of light - 4-6 wpg. Now note the positioning of one of the Anubias groups in that tank - close to the surface, right under the light. I can bet that there isn't a single spot algae on that Anubias. Unreal.

Do you have an experience with running a lean system?
Is it a question of making the plants adapt to such an environment?
Any other thoughts or questions?

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An interesting question, Nikolay. Before I go any farther, can you tell us what you think a "fat" system is?

Roger Miller
Roger Miller said:
An interesting question, Nikolay. Before I go any farther, can you tell us what you think a "fat" system is?

Roger Miller
a 'fat' running system is a tank where dosing is done by teaspoons of dry chemicals. Where water conductivity is in hundreds of uS. Water with tons of useless sulfate, chloride, sodium and other minerals.
In a 'fat' system, nutrients must be dosed at elevated levels to be accepted by plants.

That's interesting, Edward. I (and a lot of other people) have tap water with conductivity in the hundreds of uS/cm. We even grow some pretty nice tanks. Luis's "lean" tank that Nicolay was referring to almost certainly has conductivity in the 100's, since the stuff that comes out of the tap in Houston is hardly rainwater. In fact, by your definition, sea water would make an inherently and hugely "fat" system.

I thought Nicolay was referring to N and P levels.

Roger Miller
You are right,
the most beautiful tanks out there are tanks with tap water.

One of Nicolay's issue (mine too), is to limit water changes to a minimum.
Nico said:
Later I started dosing my tanks heavier and some did great and some had problems. The common things for all of them was that I had to keep up with the fertilization and water changes or else.
We all know, that dosing heavily with unconditional weekly water changes work great.
Now, changing 50% water in a 15 gallon tank is quite fine, but maintaining several larger tanks like 130 gallon week by week? There is no more time left to enjoy the look of the tank.

This is why we are looking for an alternative.

For example,
I fill up a tank with RO water run once over a dolomite bank, the water is 40uS. If I dose once NO3 10 ppm, PO4 1 ppm and K 6.6 ppm I get 70 uS. A week later, there is still 70 uS and the nutrient ratio is off. Only option left is water change again.

But, if I dose daily NO3 0.1 ppm, PO4 0.01 ppm and K 0.066 ppm, a week later, there is 40 uS. No need to do the water change. The added nutrients are consumed without leaving anything behind. No contamination, no need for a water change.

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You don't have to dose your tank to 10 ppm nitrate every week and do 50% water changes to keep salinity under control. In fact, don't dose anything to your tank unless the plants need it, and then only dose what is necessary to get healthy, attractive growth. If you think you need to add too much to keep the plants healthy, then reduce the lighting or get rid of the plant that is most limiting..

Once you figure out what the plants need then just maintain that routine. Stability is a good thing and using frequent small doses may promote stability.

The problem here is that setting up this sort of minimalist dosing procedure is a trial-and-error process based on reading and interpreting nuances. The trials are useful, but the tank might take a long time to recover from the errors. Experience helps a lot.

The big dose, big water change method is a cut-and-dried (but not simple), cookbook method that is less subject to problems. If you don't have the time to trial and error your way to a 'lean' dosing procedure then maybe the big dose, big change method is better.

Roger Miller
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My question is why is leaner better?
Examples of bad growth is more common and algae can be found in both cases. But good growth is not hindered by richer N & P.

If you want less growth, add less light.

Why set the system up to crash if that is goal to avoid?
Less light and leaner will be a better mix than high light and lean.
Lots more wiggle room.

Given plant enzyme (both induced and constituative) transporters, I think a high concentration rather than a lower level would grow better plants.
I can also show this in terms of uptake.

I can grow plants just fine at high levels of light and rich N and P.
I just gave away a lot of plants to over a dozen people tonight.
My tanks had no issues. I have not been pampering them at all.

You can limit growth with less but not too little so you can crash either method as easily IME/IMO.

Some folks just have trouble keeping things stable. Some don't.

The issue is getting plants "use" to a routine and then maintaining that routine.

So which is easier to maintain?
Water changes and dosing is easy.
Critical low levels and rich substrates(which can pull junk into the water column when pruning) seems more troublesome.
Less light will help, not adding more.

A good aquascape does not mean a good method either.

If your goal is stabilty and nice manageable growth with plenty of wiggle room, try 2 w/gal, a decent fish load, algae eaters etc, CO2 and relatively consistent maintainance and dosing.

I've had high light tanks for 10 years. Lean works better at lower light.
You can crash easily at high light also.

Well you just try it for awhile and see for yourself.
But try to look carefully at your plants and note the biomass also in the tank.

Tom Barr
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plantbrain said:
... try to look carefully at your plants and note the biomass also in the tank.
I think that plant mass in a tank is a key issue when considering lean tanks. If you are striving for rich, lush, luxuriant and dense growth trying to stay lean may be counter productive. However, if you want unplanted open sand and a sparse natural look then lean is probably better. I have never dosed my tank to 10 ppm NO3 and have had some nice looking and very stable tanks to show for it. I have had trouble when I wanted an overgrown super lush look; and I have found that the leaner I go the more likely I am to have problems with a particular species of plant failing when my species selection is diverse. Rich dosing, as commonly associated with the estimative index, assumes a desire for bursting lush growth and super diverse species selection with minimal troubleshooting.

Although light limitation can serve to create a lower maintainance tank, a lean tank doesn't necessarily require less light. I think your just enough, just in time, with minimal water changes is an interesting project. Go for it and let us know what you learn.
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