"Mark Trueman" wrote in message
...
PH with co2 injection in my tank is about 7.2

According to my calculations, your KH as CaCO3 is 26 degrees, which
would
give you 49 ppm CO2 with that pH. If that's correct, it's a little high.

I have conflicting readings, my water authority gives me that value of
289ppm (which i work out as 289/17.86=16.81dKH using the formulae on
http://www.thekrib.com/Plants/CO2/ha...arryfrank.html) but when i
test
kh with a test kit from the tap it comes out at about 13 dKH which i
believe
is about 22 ppm co2. Id rather go with a test kit of my own water. Im only
bubbling 40 bubbles a minute into my eheim so i cant see that i would be
able to get 49ppm with that, even if my kh was 26. Im probably one of many
who doesnt quite understand kh/gh. My kh test kit says 13 so thats what im
going with!!

Yeah, I kind of suspected that might not be right because it's unusually
high. KH test kits measure alkalinity as CaCO3, not HCO3. The ratio of the
atomic weights of CaCO3 and HCO3 is about 1.6, so the alkalinity in the
published water analysis is really 473 ppm, or 26 degrees. But yes, I would
go with the results of the KH test kit, as you're doing.

Are those symptoms occuring on new leaves or old leaves?

Its old leaves, so you suggest a possible lack of macros. I think most of
my
macros are in abundance, the only one i dont test is K and i add about
20ppm
per week of that.

Well, in that case, Chuck Gadd's nutrient deficiency article at
http://www.csd.net/~cgadd/aqua/art_plant_nutrient.htm suggests it might be
the magnesium as well. That's one more sign that your plants are lacking Mg.

You also say about increasing my trace mix dosage. Im worried about too
much
iron, my current dosage has my iron at about 1ppm currently which i think
is
a bit too high. Maybe this will decrease faster as i add mgso4; the
trace+iron will be taken up by the plants at a faster rate, keeping the
iron
levels down.

The iron test kits are not really useful for determining how much iron is
available to plants and it's unclear what kind of iron they are measuring.
Other hobbyists keep Fe at 1.0 ppm without problems. I add about 0.7 ppm per
week to my high-light tank, and it never measures very high. But if you say
that it's the old leaves that are affected, try adding the Mg first before
increasing the traces. And keep up that PO4.

How much Mgso4 do i need to get to the 50ppm you mentioned? Those
calculations throw me!! I think its about 14 tsp a week (using the krib
pages) in my tank of 160 litres, maybe you could confirm this. Seems like
a
lot of mgs04.

The quick way is to just add the dry MgSO4 gradually until your measured GH
increases by 2 or 3 degrees. It's definitely not 14 tsp a week. For my
30-gal. tank, one mL (1/5 tsp) of dry MgSO4 by volume increases the GH by
one degree. You could also use Chuck's nutrient dosage calculator at
http://www.csd.net/~cgadd/aqua/art_p...osage_calc.htm to make an MgSO4
solution.
__
Alex
pcalex (at) hotpop.com