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Re: pearling question

>From: "Beard, Kelly" <KBeard at comdata_com>

>I've noticed that my growth has slowed on some plants and completely frozen
>on others - plants won't bubble.  I'm changing water every week now, 20
>gallons worth in a 75 gallon tank.  I use 1 Duplaplant tablet, 1/4tsp of
>Kent's RO right, and 1/4 tsp of baking soda for every 5 gallons of RO water.
>I mix this up in 5 gallon jugs which usually sit for 24 hours before water
>Whenever I do a water change, my plants will start their bubbling.  As the
>week wears on, it stops happening.  I'm using CO2 constantly, about 20ml/L
>(I think that's right), 12 hour photoperiod.  I use Dupla drops in between
>water changes.  I have laterite in bottom 3rd.  220 watts VHO URI AquaSuns.
>I'm beginning to think that I might be missing some nutrient.  My iron
>levels are good.  I use the LaMotte iron, CO2, and nitrate test kits.  I
>never get any measureable nitrate (at least that I can see) or phosphate
>(Seachem).  Nitrate and phosphates are not added during water change, so
>what 'thing' is making my plants bubble at water change?  Is it an excess of
>CO2 coming from the 'fresh' water, or some nutrient that is lacking that the
>plants get from the Duplaplant tablets?  I did not notice a drop in pH when
>I added the water (I have a meter to keep this in check).
>I guess my question is - at what CO2 levels do plants 'pearl'?  If my levels
>are good, then what nutrient might I be missing?  How do you guys know how
>to dose an individual compound, like epsom salt or potassium or whatever?

Try an experiment.  add the Duplaplant tablet, the 1/4 tsp of Kent's RO
right, and the 1/4 tsp of baking soda directly to the tank without adding
any water.  See if the bubbling rate increases.  Or, you could add the RO
water without any additions and see if there is any increased bubbling.
Either way, the results would indicate whether the mineral additions to the
RO water is stimulating the increased bubbling or not.

Given good light and good CO2 levels, plants will photosynthesize a lot
more if they have all the nutrients they need than they will when one or
more nutrients are short.

Paul Krombholz, in sunny, spring-like central Mississippi