[APD] Re: Nutrients, Water Changes, Etc.

["William M. Cwirla" <wcwirla at verizon_net>]

As a planted tank "enthusiast" (I refrain from applying to myself the 
venerable terms "aquatic gardner" or "aquascaper") who lurks happily 
somewhere between Barr Level 1 and 2, I am chiefly interested in a 
small number of tanks that look good over a long haul with a minimum 
amount of work.  A few observations for what they are worth:

1.  High nitrates (>100 ppm) seem to slow growth to a crawl.  I had two 
tanks that went way over the top in nitrates (let's not discuss why, 
OK?).  As soon as I brought the nitrates down to below 40 ppm, plant 
growth resumed with a vengeance, especially my dwarf hygro which 
sprouted dozens of side shoots and turned into a shrub.  Fish seemed to 
appreciate it too.  Lesson:  watch those nitrates, especially in high 
fish load tanks.

2.  I'm wondering about long-term build up of residual salts due to 
regular dosing of fertilizers.  Most of the nutrients we add are 
chloride or sulfate salts.  While the potassium, magnesium,  etc. are 
utilized by the plants, the counter ions are not (except in the case of 
KNO3 or KHCO3).  Presumably, there will be a long term build up of 
sulfate and chloride salts in the water column.  A 50% water change 
will not offset the additions.  Which leads to a thought:  For long 
term stability, perhaps a huge water change, say 50% daily for a week, 
a couple of times a year, might help to "reset" the tank to its 
starting parameters might be in order.  When I battled a green water 
plague in a 29 gal, I did daily 15 gal changes for two weeks.  The 
ensuing plant growth was remarkable.  I've noticed that over the years, 
my tanks seem to "slow down" in terms of growth and vitality.  Should 
we be thinking in terms of a "rainy season" for our tanks to flush them 
out?

3.  Recently observed an interesting nutrient deficiency.  My water is 
fairly hard (13 dGH).  My L. repens was showing signs of Fe deficiency 
(correcting the high nitrates caused the Fe to plummet from 1 ppm to 
almost undetectable).  After correcting the Fe, the plant was still 
having trouble - rapid, though pale pink new growth, brown holes and 
yellowing of old leaves with premature leaf loss.  After a bit of 
netsearch, I discovered that L. repens is sensitive to high Ca/Mg 
ratios.  One change I had made was that I was dosing Fe/traces using 
Homegrown Hydroponics chelated trace mix, which has no magnesium.  The 
addition of a small amount of epsom salts corrected the situation 
almost overnight.  The new growth is turning red with some green.  
Thought:  Even with hard water, you might run into magnesium deficiency 
if the Ca/Mg ratio is not right.

Your thoughts are always appreciated.

WMC

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