Hair algae (I need help!)

Yes, you can certainly counteract the dark cycle reactions's (plant respiration) production of CO2 with an airstone on a timer, but remember that you still want to maintain a CO2 level of about 25-30ppm. It sounds like you've got a pretty awesome system (being an instrumental analyst, I'm incredibly jealous) so I'm sure that you can set it up so that the airstone degasses excess CO2 if it rises above 30ppm and stops degassing when CO2 levels fall back down.

If the plants aren't pearling it's a sign that your water is less than supersaturated with O2, either a sign that CO2/lighting is low, which isn't likely a problem, or that your plants are struggling due to a nutrient deficiency. You describe what could be a K deficiency: http://www.csd.net/~cgadd/aqua/art_plant_nutrient.htm
You should be dosing K already since you get so much NO3 from your tap, sounds like you need to increase the dose or frequency of the dose.
 
Thanks for the comment about my set-up, about three years ago a did a half-assed attempt at a plant tank which failed miserably and when I stripped the tank I decided the next time I did it I was going to do it right from the start. But expensive equipment can not overcompensate for lack of experience. It does strengthen the ressolve to see the problems through, knowing you have so much expensive equipment that is worthless for anything else. Being an electrician also helps in the controls aspect (it is actually fun figuring out the mechanical end of things)( I also enjoy the challenge in trying to understand the chemistry, cause and effect)

I would trade all my equipment for a fraction of your knowledge any day!

As for the K, I dose daily about 1.35 ML (per the labeled instructions)
Kent Botanica - label reads 5% soluble potash (K2O)
How much should I increase this?
Should I use a different kind?
 
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There are three possible cases depending on your interpretation of the label.

First: It means 5% available K.
In this case your current dosing adds 0.2ppm K to your tank, you're aiming for 20ppm, so in that case you would need to dose 136mL

Second: It refers to K2O but the 5% only applies to the two K's. In that case you're providing double the first case, 0.4ppm and should instead be dosing about 68mL.

Third: (most likely in my mind) It refers to 5% K2O by mass
In this case the solution is about 4.15% K (K makes up about 83% of K2O by mass)
This would require an addition of 164mL to produce 20ppm.

I don't know how big your bottle is, but I suspect that this would be inordinately costly to implement.

Instead, get some KCl (check your grocery store for "NuSalt" or "NoSalt", just make sure that it's all KCl, not 50/50) and add about 2.25 tsp. to your tank, dissolve it in some water first.
 
Is there any economic way to measure the K levels? I was think about getting the lamottes colorimeter but without a specific need I cannot justify the cost. Most of the test kits seem to be Ok, but do have their limitations.

The K I have is a 435 ML bottle, once I initially apply the large dose you reccomend, What should be my dosing schedule after that? or is that a daily dosing?

I have K2so4 powder, would that work as well? and how much should I use if so.
 
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If you've got K2SO4, you're all set. Download Chuck Gadd's nutrient dosing calculator. I don't know the full link by heart, but it's the first "article" in his articles section, it kinda takes all the work out of calculating doses.
www.csd.net/~cgadd/aqua

There's no economical test kit that I'm familiar with. Part of the problem is that we don't test for K on a regular basis in Oceanography (I can't speak for the Limnologists, but it's likely the same), so any kit would have been developed specifically for the hobby, and that means $$. Any K testing that's done would probably be done electrochemically anyway since element specific probes are generally much easier and faster to use than wet chem.

As for a dosing schedule, it depends on your uptake rate. My approach is to dose to the desired concentration at water change then do a half dose every other day. For KNO3 in my 33g I dose 10-15mL (I made up the solution so that each mL increases NO3 by 1ppm) at water change then a generous 5mL on alternate days. I dose traces on the days that I don't do macros. But I came up with that empirically, by testing I discovered that my KNO3 concentrations fell from about 10ppm after the initial dose to roughly 5ppm (it's tough to gauge the shade of pink) in 2 days.

Given your setup, it's fair to assume that you've got fairly high uptake and I suspect that a similar regimen would suit you quite well.
 
I just want to check before I do anthing crazy, I went to the site you mentioned and based on the table it recommend 8.3 tablespoons of K2SO4, Is this correct? I do not want to overdose and hurt the plants or the fish.

I used 90 gal as the size and 10ML to mix it with, that gave a result of 19.77 PPM for the K2SO4.

Why do the numbers change so radically when you alter the water to mix number?
when I typed in 10 ML to mix with 150 grams, it gave me 19.77 ppm
but when I typed in 50 ML to mix with 150 grams, it gave me like 3.95 ppm?

why so different (ppm) for the different mixing amounts?
 
Ah! there's the problem. When you tell it what volume to add it to it thinks that you're making a stock solution and then tells you by how much each 1mL of this stock would increase the nutrient level in your tank.

For potassium it's easiest just to click the radio button that says "add dry compound directly to tank" beside it. You should get about the right concentration with 2.75tsp. Of course when it sais "add dry compound directly to tank", what it means is dissolve it in a little water and then add all the water.
 
I used the measurement you recommended for the KS2SO4, how often should I dose that much?

Also it has been several days since the plants have pearled well. why in the past even with the K defficient were they pearling nicely and now almost nothing?

I cannot find anything out of the ordinary, is there anything I could be overlooking, or should I just wait a couple days now that I dosed the K2SO4?

I will be happy when this tank finally stabilizes. Although I don't know what I will do with all the extra time I would have.
 
Re-dose half that amount every other day, dose the full amount after your weekly 50% change.

I suspect that the plants were growing strongly using up stored nutrients and making due with what was available as best they could. Now they've used up their reserves and now are relying on what's in the water column so it's very important to provide them with what they need.
 
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