Plants and diseases, muriatic acid, iron levels

Karen Randall wrote: 

<"IMO, it is better to avoid illnesses in planted tanks.  I _nver_ 
add medications to my planted tanks.  I quarantine new fish, and 
in the rarte instance that a fish _does_ become ill, it is removed 
from the tank if medication is warranted.  The introduction of 
most diseases can be avoided with forethought.">

Hygiene is unfortunately not a 100% guarantee. The introduction of SOME disease
can and should be avoided. A properly conducted quarantine is a must and gives
the possibility to observe quickly progressing diseases that were in incubation
phase at the moment the fish was purchased. However, slow-progressing problems
or sub-clinical infestations are often missed during quarantines.  
The situation is not as cut and dry as you present it. The use of hospital
tanks is appropriate  when you are able to diagnose diseases with low or no
transmission risk. If there is a reasonable chance that the whole tank is
infected, its whole treatment may be a very valid approach in many situations.
Plants may or may not be affected by this treatments, and more information is

<"the question is why were there sick fish in your tank to start 
with.  In my experience, healthy fish put into a healthy planted 
tank _rarely_ get sick.  Even when they do, it tends to be an 
isolated occurance... for instance, a single fish damaged in some 
way, or perhaps very elderly, that succumbs to an infection.  It 
has literally been years since I've had any sort of infection that 
spread from one fish to another in a planted tank. (Incidentally, 
in that particular case, it was a disease that came in with some 
wild-caught West African fish which I had quarantines, but 
obviously not for long enough... I ended up having to tear down 
and sterilize the tank) :-(">

The problem is to recognize healthy fish.It happens that the sick fish I have
is (probably) wild-caught green discus, likely to be affected by highly
transmissible parasites which may also colonize for a long time their host with
no symptoms. There is no way to know if they all came in  all carrying
parasites, or if the problem spread in the planted tank. All fish in the tank
had been quarantined for at least 3 weeks at the time of purchase, and treated
prophylactically for the most common parasites.They were perfectly fine for
about 6 months. 
 A complete elimination of all potential pathogens is  just wishful thinking
and the concept of "sterilizing" the tank is quite exaggerated and often used
Unless you destroyed all the fish and the plants that you had in your infected
tank, chances are that after you teared down everything, you re-introduced with
the same fish and plants some potential pathogens in your new "sterilized"
set-up. However, you must be very good at keeping stable, healthy conditions,
and your tank's pathogens stay quiet most of the times. Equilibrium is the key!
A lot of stress to fish, plants and aquarists could be avoided if impulsive
complete tank break-downs were replaced, at least initially, with a more
careful evaluation of the pathogen-host interaction, and of all the options
available for intervention. Every solution has its risks and benefits.
The concept of fewer diseases in planted tanks is certainly fascinating.
However, an association of facts does not necessarily imply a causality. For
example, your fish may just benefit from the very good water conditions you
keep in your tanks for your plants. Equivalent water conditions without plants
may be just as good. This is just an example, not an opinion.  It would be very
interesting for me to see some postings with reference to research data.   

<"Muriatic (hydrochloric) acid. ">

Would it be possible to know how should it be used in the aquarium (dose,
possible problems with it, etc.)? Thanks.

<"Maybe I missed 
it, but I haven't seen enough information for me to hazard a guess 
why your iron levels are so high.  It doesn't sound right.">

Exactly on the basis of what you said, couldn't it be thought now  that the DAI
tablets are also the main reservoir of the Fe leaching in my tank?

<"You have to understand that this list is a group of fellow 
hobbyists who are here to enjoy each others company and exchange 
information.  Everyone here has "real" lives and responsibilities">
It did not even remotely cross my mind to make a complaint about lack of
responses to my postings. As a matter of fact, I have received several
responses on various issues. You do not need to bend the meaning of my words to
point out how many generous people are on this list. It is very evident! 

<"For those who want to experiment, that is their choice.  IMO, it 
is best to use the tried and true methods until you have succeeded 
with them.  Once you have mastered the basics of planted tank 
maintenance and have some experience under your belt is the time 
to branch out into experimental methods.">  

Very true.   

Thanks in advance to all those that will provide comments and suggestions.