Nutrient deficiency...how long to show up/go away?

[newfound77951]

Am still figuring out this nutrient dosing business....

All my plants are now doing pretty well, the algae is on the way out (how long does it take for hair algae to disappear??) now just resisting the urge to mess with the aquascaping and let everything grow a little.

My question is, one of my big swordplants (E. cordifolius or something similar) started showing signs of potassium deficiency (yellow/brown tips on the old leaves). I dosed 15 ppm K about a week ago and then again 3 days ago. The affected leaves don't seem to be getting worse, but in between the two doses some of the new leaves are turning yellow between the veins, which would possibly indicate Mg deficiency....or is it just the lasting effects of the K? How long does it take for deficiencies to show up, and how long after dosing should the symptoms stop or go away? All the other plants seem fine, one other sword got a new leaf that is all crinkled up but it was in a low-light, non-fertilized aquarium for a while and that is probably the cause.

If Mg is to blame, then I will dose that too...ran through the calcs earlier and was getting some weird numbers...do you usually have to dose multiple grams of MgSO4 to get 10 ppm in a 55 gal?

Oh, sorry, here's tank params:
55 gal, set up for 1 month
2x96w PC
Eco-Complete
AquaClear 70 HOB
2x DIY CO2 with Red Sea reactor
Dosing: CSM+B (PMDD mix so has some K, N and Mg), 5 ml Excel every day
KNO3 as needed to ~20 ppm (just figured out my test kits are lousy at low ppm, probably had no NO3 for a while, hence algae)
KH2PO4 as needed to 0.5 ppm (to help get rid of rampant algae)
K2SO4 15 ppm 2x a week

Thanks for the advice! This is so fun!

 

[czcz]

Trace deficiency can show up and go away quickly ime, especially with a fast grower. Hair algae seems to take at least a couple weeks to beat after addressing the deficiency -- as long as you've stopped it from spreading, you're on the right track.

I've no experience with your sword, but it does sound like a K and trace issue. How attached are you to the PMDD mix? Would suggest omiting KNO3 from the solution so you can just dose traces higher while adding K. If you are using the standard mix, and omit KNO3, it would be a good idea to dose 25mL with your light to reach ~.2ppm Fe while increasing Mg. If you do have Mg deficiency, increasing concentration with other traces should address it. Tom Barr often says a little Mg goes a long way.

Of course you would then need to add KNO3 dry or in a second solution, but it appears you are doing that already. HTH

 

[newfound77951]

Thanks...sounds like I have another deficiency besides the addressed K. I cannot get my iron test to read anything, no matter how much trace I add...I have a Red Sea test...could I really be going through 0.1 to 0.2 ppm per day or is the test kit lousy? Are there better ones?

 

[Purrbox]

Unfortunately the only Test Kits that will give a good enough reading for iron at the levels we need will cost you an arm and a leg. Same goes for Potassium. That's why for a lot of the nutrients it's recommended that you judge based on your plant health instead of using test kits.