Magnesium

["Matthew Simmons" <matt.simmons at ntlworld_com>]

Mark Truman wrote

" ..... I would have thought my phosphates would be lower and that this is probably

what is causing the BBA. Im going to stop dosing this until my phosphates

get a bit lower. This is my main priority; i want phosphates to be the

limiting nutrient in my tank. Currently it seems to be something else.

Ive also notices that some of my leaves are developing yellow edges and

brown veins which i initialy thought to be due to iron deficiency. Turns out

that this isnt the case (assuming a valid test kit) so i'm led to Magnesium

(or lack thereof) preventing the uptake of the iron.

QUESTIONS

Is it more than likely that magnesium is what im missing??

If so, what ppm of magnesium do i need to aim for?, How much epsom salts

would i need to add to my 160litre tank to hit this amount?"

IMHE, Mark your problems are almost certainly a Mg deficiency rather than iron. I struggled for a year using water with similar imbalance between Ca and Mg. I followed Michael Rubin/Tom Barrs regime (great advice from both - thanks) of good C02 good K and good NO3 but still suffered low growth and the sort of yellowing of leaves as per your images but much worse. I also had a major BGA problem that would never go away in fact it was the only stuff that grew in my tank! I will be honest that although I suspected low Mg, and this was corroborated by a report from my water company, I never really got the balance right just with adding Epsom salts and I believe the balance is crucial.

My understanding is that without this balance between Ca and Mg, there is poor K uptake which manifests itself in terms of yellow (old) leaves and dropped foliage. Hence K deficiency symptoms when there is clearly adequate K present. If you want to go the Epsom salts route there is an excellent calculator on Chuck Gadds site http://www.csd.net/~cgadd/aqua/art_plant_dosage_calc.htm.



Personally I eventually solved my problem by reconstituting rain water with Seachem Equilibrium. I was never sure that the tap water supply was consistent enough - its undrinkable and one day you cannot see through it and the next its clear. For me using tap always gave problems hence using rain water amd Seachem, I always know exactly what I am dosing. 

I would also look at your Co2, BBA can also indicate suboptimal levels of this and your pH seems high - again check Chucks site for the calculator.

My advice for what tis worth - keep dosing as you are with everything and add Mg to at least half the level of the Ca, up your CO2 a tadge and see what happens.

Lastly the brown streaks in your new Echinodorus leaves - new leaves quite often tend to show reddish colouration - IMO this is quite natural. Enjoy it, I think they look neat.

I hope this helps.

Regards





Matthew

In sunny Hampshire



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