Results of dosing potassium

[Allen_1971]

Yes I know Suplur is a macro nutrient, but its critical concentrations are 10x lower than that of potassium (ref ecology of the planted aquarium).

So for example, if you dump 20ppm of K/week, you get roughly 16ppm of S. Assuming your plants consume all 20ppm of K, and if the book is right it will also take roughly 2ppm of S. Which leaves you 14ppm of S. Now assuming the S stays in the water column, and you do a 50% water change weekly, that still leaves you with an accumulation of 7ppm S.

If this process goes on weekly, your overall levels of S will be going up and up. which is my worry...

Once again, I'm not sure on this... I'm just trying to reason out what happens to the sulphur. There could be some chemical reaction which changes the SO4 to some other non harmful state... but as I was a lousy chemistry student, I'm not going to try and venture there... Perhaps DEA could have some input?

[CK Yeo]

Critical concentration is the lowest concentration of a particular element before a deficiency symptom appears. It does not necessary mean the concentration that is taken up by plants or the concentration in the plant.
Would you happen to know what is the S toxicity concentration for plants and fish?

In anycase, a change of water will dilute out whatever excess (not just S) that might build up over time.

ck

[bclee]

Allen, according to your scenario, by keeping up with 50% water change, you will never exceed 28ppm.

BC

[Allen_1971]

Yes... I was looking at it and it lookes like the curve has some form of tail off point... but that assumes that the water change is 50%. Typically I do a water change of 30%... Lemme go do some excel calculations to see what the curve is like...

Oh as for the critical concentrations, yes I agree its the minimum levels. I'm making the assumption that the minimum levels also roughly dictate its intake levels (which could be wrong).

Will post back in a bit on how my cals go.

[Allen_1971]

OK I've done the cals and I realize that there was an earlier error in my assumptions... Potassium Sulphate is K2SO4... meaning 2K and 1S... so the ratio of K:S is not 100:82 but more like 100:41

Anyway, based on this, I've done some calculations based on the following assumptions...

1. Enough K2SO4 is added to raise K by 20ppm weekly
2. A water change is done weekly
3. All the K is absorbed each week, and S absorbtion level is 10% of K level

Based on this, the level of S tails of after 15 weeks and reaches 20.5ppm for 30% water change, 15.5ppm for 40% water change, and 12.4ppm for a 50% water change... So water changes look critical to keeping your level of S low....

Now of course the critical question is what was asked earlier... at what levels does S become dangerous to fish? All in all, I would say that my mind is much more at ease since the level of S does go skyrocketing out of control... Looks like K2SO4 is the way to go

p/s If anyone wants my calcs... pm me and I'll send to you... hehe you can spot any mistakes i made [] [] []

[wahboy]

hello gang,

from what i read in APD, the sulphate levels in our tanks due to fertilisation and water changes will not harm the fish or plants. it takes a lot of sulphate to do anything to the livestock and plants.

hope this helps.
Wahboy

[DEA]

*cough*

why make life difficult for yourself?
whenever i find myself itching to calculate how much of what is where, i just go ahead and do a water change
like bc pointed out, water changes will make sure nothing will accumulate in great amounts

[PeterGwee]

Do more water changes in a week and dose at the end of the week...Mmmmm..should keep harmful nutrients to a minimal...[]

[vinz]

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On 11/30/2002 12:49:25 AM

Hi Vinz,

How's your planted aro tank doing?

...

Cheers,

Kenny
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Hi Kenny,

Welcome aboard! Guys, Hobbit6003 is another guy with a planted arowana tank, started about half a year before mine and Vican's.

Kenny, you've been into planted tanks for quite a while right?

Anyway, my tank recovered from greenwater after a few water changes and a blackout early last week. The NO3 dropped to about 30ppm from some value way beyond 40ppm. This weekend the water turned cloudy again, but the NO3 was at an amazing 5ppm and PO4 at 0.5ppm. This morning the water cleared by itself after 3 days.

Suspecting bacterial bloom (after speaking to Chan at NA) which could mean the bacteria colony was damaged by the water changes the week before. Now I'm wondering what the NH3/4 and NO2 were like in the last few days. Got to check NO3 again tonight.

Other than that and an incident where the a greedy SAE got gobbled up together with the market prawn, nothing much happening to the tank.

[hobbit6003]

Hi Vinz,

Thanks for your welcome! Yes, I've been into planted tank for the past 4 years now, and it was this Feb that my hands and brains got itchy, and decided to get an aro to mess up my tank![]

I'm getting my black brush algae under control now, thanks to the removal of the feeder goldfishes, which had elluded me until last month, and also the addition of the distichodus sexfasciatus as an algae eater, which incidentally do nibble some plants and eats market prawns too.

I'm still registering a NO3 level at about 20ppm, and I've not measured my PO4, but think is high as even my nuphar japonica flowers.

The tank is also seem to be very dusty, and most of the old echi leaves are covered with dirt and a velvety kind of algae.

I'm using geoliquid for planted tank now, and it seems to have perked up the plants and aro at the same time. I used to clean the glass of green algae film every 2 days, but now it can be stretched for nearly a week. Of course, I do occasionally supplement that with Dennerle V30 and E15.

Now, I'm thinking of boosting the uptake of NO3 and PO4 with addition of K2SO4 or KCl, something I used to add but I threw away the solution unwittingly. When I was dosing the extra K, I do see lushier growth and the water surface highly polished and glistening.

How big is your aro now? Mine is 15 inches and growing, and I cannot wait to do my 8 fter next year, yes!

Cheers,

Kenny

[vinz]

He's about 10 to 11 inches now. The gold is starting to show.

[FC]

Hi arowana keepers,

I have not tried aro in planted tank but very keen to have one in future. May I know what do you feed them, I mean for the good of both the fish & the plants. How much & how often do you feed them, say, for a 1 feet sized one?

Thanks.

[vinz]

Well, I'm feeding my arowana solely on market prawns right now. Will try pellets on him soon. No live food because I don't want him to get used to eating live prey and start chasing my algae crew.

My RTG is about 10 to 11 inches right now. He can handle about 2 to 3 inches of market prawns a day.

[loupgarou]

I know that for the saltwater in the sea, so4 levels are at 900ppm, so toxicity levels should be way above that.

[Allen_1971]

hmmm but that would apply to marine fishes... what about SO4 levels in lakes/streams/rivers?

[FC]

Concern on over accumulation of SO4. You may wish to consider my method:

<Adding potassium by using Potassium Sulphate, K2SO4 (45%K & 55% SO4)>
Add 7g per 20-30% water changed, say 100 litres. That would give about 31 mg/l K+ and 38 mg/l SO4 for that fresh water.
-what about the old water? Do not bother, with each water change, K+ would increase gradually. For the first dose, the tank would end up having about 10 mg/l on top of the liquid fertilizers.
-the logic: assume no uptake of K2SO4 at all by the plants/fishes, the tank would end up close to 31 mg/l K+ and 38 mg/l SO4 after many months/years of the above mentioned routine; the water column will never exceed 31 mg/l of k, 38mg/l of SO4 (or 10mg/l S).
-in real life: the plant will consume pretty much per week and after a few months of the K+ regime, the tank would likely to end up having average of 15mg/l. At all time, SO4 will also be kept well below 38mg/l or S at well below 10mg/l.

Have fun.

[hoppinghippo]

Can someone help with the calculations for 60L tank? if I change1/3 water each time, that'll be 20L. assuming I want 25ppm, how many grams of k2so4 must I add each water change? cuz I think when I first add it should be a large amt and each water change should be much smaller amts rite?

[Allen_1971]

not necessarily... the problem with dosing K is that there are no easily available test kits for checking our K levels. Fortunately, K levels can reach very high levels and still be safe in aquaria. Even better, K is one of the highest consumed nutrients by plants.

for me I typically just doss the full amount (20-25ppm) each week.

Theres a simple calculator on Chuck Gadd's webby which can help you in your dosing calculations

Calculator

[vinz]

Nope, each time you dose the full amount. 1 teaspoon of K2SO4 per 100l of water will dose about 27ppm of K.

You can use this calculator to calculate.

[Vican]

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On 12/31/2002 11:32:12 AM

Nope, each time you dose the full amount. 1 teaspoon of K2SO4 per 100l of water will dose about 27ppm of K.
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So how much do you dose a week? The amt for the water changed or the amt for the whole tank volume?