[APD] RE: Fertilizing a new tank(when to start)

[Thomas Barr <tcbiii at earthlink_net>]

>"Why do some suggest reducing nutrient input during start-up?"

>Difficult to answer since we don't know the entire protocol of the
>alleged suggesters; whether nutrients are non-limiting with their
>strategy when they are supplied. There is an hypothetical growth rate
>limit for plants even when all nutrients, light are maximized and other
>confounding factors, such as toxins (metal ions) and nutrient imbalances
>are minimized.

I'll assume that algae is non limited. 
This is the main reason they suggest for not adding the fertilizers.

I know algae and I know fertilizers, so I am trying to understand the logic behind it, so far I've not had/heard any arguement to suggest my reasoning is incorrect. It would have to suggest that NO3 and PO4, Fe etc cause algae if they are in excess. New tank, old tank, what is the difference?

This is clearly not the case. 
I am curious as to why a plant that is limited will be better/healthier/have a faster growth rate than a non limited plant. Even if the roots are healthy and actively growing. 

We prune and keep fertilizing each week, we cut the roots off. Replant the tops etc. Should we not fertilize for a week till the new roots grow in?

I just don't buy that.

>If you are starting up, the smaller plant mass may not require as many
>nutrients, in particular nitrogen so the supply of nutrients available
>to bacteria and algae is greater. Yes, bacteria and algae do grow faster
>when nutrients are more concentrated, particularly when N or P are
>"excessive". It may be easier during start up to maintain a proper
>balance by using less nutrients (not ceasing them entirely) but in
>particular nitrogen and phosphorus.

So algae are "limited" under this notion?
I don't think so. Perhaps with respect to availability of NH4, but I can say that PO4, NO3, Fe etc don't cause the blooms.

So I ask the question, "why not fertilize with these nutrients in a new tank?
Biomass will not matter to some degree with respect to NH4, as long as the NH4 is being removed, then the biomass of plants is less/not critical.

10 plants or 1000. Won't matter if the NH4 is nil and they are able to remove it all.
Adding the other ferts will help increase NH4 removal and uptake.
New or old tank, it makes little difference. 

>If you are using an organic soil tank, then it may also be very useful
>to perform more frequent water changes to reduce the amounts of organic
>nutrients in the water since these contribute to algae growth more so
>than elemental minerals. We have to be specific about which nutrients
>we're talking about.

Well, goes back to NH4:) OM and soils have this component. Remove the Urea/NH4 , then try this. 
You'll see a difference.
You could argue more frequent water changes will do a similar thing in a Flourite tank also.
NH4/urea production rates are the issue, less so for the other nutrients. 

>For an organic soil tank, I think you should
>reduce N & P but maintain all other nutrients at the steady state target
>levels.

So do you dose NH4 or something?
Most folks only dose NO3, PO4 etc, not NH4.
So reducing these NO3, PO4 levels are not going to influence things if you induce the algae with NH4 to begin with.
Therein lies the problem.

>Perhaps the most interesting question, if I reframe it, is whether root
>development is: will be promoted by a lower ratio of chelated Fe in the
>water or by a lower ratio of P in the water? Perhaps. Root development
>will also probably be stimulated by higher nutrient levels in the
>substrate. A lot of things are going to affect the root to shoot ratio.
>Is a higher root ratio in any way desirable? I should think it is
>favoured by natural selection in oligotrophic conditions. As Tom points
>out, aquariums are seldom oligotrophic. If you intend to never add
>chelated Fe, then a higher root ratio would be beneficial but there must
>be Fe and something like peat in the substrate to provide reduced Fe.
>The same argument can be made for P.

The same arguement can be made for :are the algae limited or not by Fe and PO4?
Roots development was shown NOT to be significant when the water column was non limiting.
You can cut the roots off and the shoot will grow the same in a nutrient rich water column. This was shown in a study done in Denmark (Madsen et al 2002).
We do this each time we prune as well. 

There are no roots yet the plants grow vigorously. What is the difference then? Bacteria in the substrate/amount of NH4/uears etc , NOT the presense absence of a healthy root system. Not because there are excess NO3/PO4/Fe in the water column.

The bacterial issues can be addressed, add mulm and peat. 
No wait, no worry. 

>s it possible to get away without chelated Fe in the water? I think you
>could have enough Fe in the substrate that it never ran short until the
>roots so filled the soil that the redox potential wasn't sufficient to
>reduce Fe. Fe oxidation zones are visible in the substrate near the
>glass as rusty oxide deposits. 

Well, if you use a porous iron rich grain, like Flourite, then the layers are less critical since the grain has the micro environment that mimics this and it well protected when you uproot and do replanting. 

>Steve P in Vancouver

Regards, 
Tom Barr

_______________________________________________
Aquatic-Plants mailing list
Aquatic-Plants at actwin_com
http://www.actwin.com/mailman/listinfo.cgi/aquatic-plants