Re: Something's missing

[Chuck H <grendel at usit_net>]

Nick wrote:

>In the last couple of months, my tank has gone through a series of algae
>blooms and crashes.  The plants are growing very slowly, so I suspect they
>are lacking something that the algae doesn't care about.
>
>Tank is 20 gallon, 55 watt power compact, fluorite substrate, DIY CO2.
>I change about 50% of the water weekly and dose with Seachem Flourish
>according to manufacturer's directions.


That's not enough traces at that light level, IME.  My 20gals (also 55W PC 
or >) get about 5ml Flourish twice a week.



>   Our well water has a very low
>mineral content and is slightly acidic.  I can use it to water sensitive
>bog orchids and carnivorous plants with no problems.


Are you adding anything to the change water for hardness and alkalinity?



>Initially, I had an outbreak of filamentous green alage.  At Tom Barr's
>suggestion, I started dosing with KNO3.  After about two weeks, the
>filamentous algae turned brown and died.  Then I went on vacation for a
>week and came home to pea soup.


Got diatomite?  A diatom filter will take it out in a few minutes.



>Massive water changes got the green water under control, but the plants
>are still not thriving.  Proserpinaca palustris turned to mush.  Ludwigia
>and Rotala Macrandra grew well for a while but then started to rot from
>the base.


You should have plenty of light, so it sounds like a traces/Fe problem.



>Hygrophila difformis is very pale and is producing leaves more
>typical of emersed culture.  Java moss is thriving; It is practically the
>fastest growing plant in the plant in the tank.  Didiplis diandra is
>growing slowly but is still alive.  Lysimachia nummularia also seems to be
>doing fairly well.
>
>The fish are doing fine, and one of the amano shrimp is carrying eggs.
>
>I have purchased some seachem phosphate to see if I have a phosphate
>deficiency.  Is it possible that the Flourish isn't providing enough iron
>or that some other trace element is limiting growth?


I'd say trace shortage is a definitely a problem in your tank.  The PO4 
will help, too, especially if you haven't already been dosing it.

Just as a point of reference, I have 3 thriving 20gals with nearly the 
exact same setup as yours (the only diff is that I have compressed 
CO2).  Here's how I dose NPK and traces in them (based on the scrolls of 
wisdom set forth by Tom Barr):

NO3 -- 5ppm twice a week [KNO3 soln].
PO4 -- 1ppm twice a week [KH2PO4 soln].
K -- extra 8-10ppm once a week [0.25tsp K2SO4]
Flourish -- 5ml twice a week

CO2 ranges from ~30ppm to ~15ppm during the day.  The photoperiod is 
10hrs...never met a plant that needs more.

Well, hope that helps you some.  Good luck and if you want more details, 
just drop me an email [grendel-at-usit.net].
--
Chuck Huffine
Knoxville, Tennessee