High NO3 and PO4: what to do?

[cheeboonyong]

Hi,

these are my tank parameters

KH: 11 dkh
GH: unknown
pH: 7 (I think, based on colour of pH indicator)
NO3: >40 mg/l
PO4: >2 mg/l
Lights: 110 W for 10 hours

My tank is about 100 litres (~25 gallons). 2.5 ft Juwel tank.

My bioload is >80 fish (ok, sounds like a lot, mostly small tetras and corys).

I feed TetraBits once or twice a day.

Fertilisation: Seachem potassium 2 mg/l per week. TMG 5mg/l per week.

What is the most likely source of high NO3 and PO4? I suspect it's my high bioload and fish food. If so, should I feed less or reduce bioload?

Some advice I've received: add more K. Some nutrient is possibly missing and preventing uptake of N & P. Is this true? How about magnessium and sulphur? Do I need to dose these in higher quantities as well?

My main concern with the high NO3 and PO4 is the high level of spot algae I get. Other than these, I've no other types of algae. But the spot algae does attack and overwhelm my moss. To a lesser extent, my glosso is also attacked and if not for the fast rate of growth, I'm sure it'd be dead by now.

[PeterGwee]

If I am not wrong...(just guessing)..your CO2 might be the limiting factor at the moment. You really need a pH test kit or test pen to test for pH rather that those pH indicator (useless in my opinion). Get your pH and let us know. For K, why not use K2SO4? Very much cheaper and easier to dose 20ppm without burning a hole in your pocket. GH in Singapore's tap water is 3...pretty good...(note that Calcium deficiency might not be actually low calcium in the water column but the fact that plants uptake rate has slowed to crawling pace as one or more nutrients is limited.)

[wynx]

Boonyong,

Too much lights you have there...Do check your carbon dioxide level. The analogy is pretty simple, carbon is the basic building block of life and therefore without sufficient carbon dioxide ,plants not making enough food and therefore nutrient uptake slow down which result in ur case of high NO23 level. This is my guess Your data seems a little skewed. Why is your hardness above 10? @ 11?

[Nick]

My exact thoughts too! KH possibly too high. Bring down your KH and then inject more CO2 to bring the pH down slightly to about 6.8.

Dun think NO3 at 40 ppm will harm anything.

[PeterGwee]

KH 11 is fine...just wonder how come it got so high? Any coral chips? Is your KH stable? Just inject enought CO2 to bring the pH down 7.0-7.2 during the lights on period for a KH of 11.

[Plantbrain]

Water changes and more water change.
That will reduce the NO3/PO4 down real fast.
With that many fish, doign 50% weekly water changes will make them much happier.
Add some floating water sprite for now and consider using CO2 if you are after a nice fully planted tank.
You can do 2xa week water changes till you get the NO3 under 10ppm.

Regards,
Tom Barr

[naturetan]

Firstly, change the water if you can to remove the excess.

Feed your fishes just enough, only once a day. Fast them for a day/week. This ensure your fishes are healthier and not overfeed.

If N & P still high, consider reducing your bioload.

To know whether you need to dose Mg, you need to know the GH value. Above 3 is fine. If not, dose with the ratio of about 4:1(Ca:Mg)

Just in case you use Baking Soda to increase the KH, consider reducing your dosage, since excessive sodium is bad for plants.

[bclee]

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On 4/12/2003 2:48:12 PM

Hi,

these are my tank parameters

KH: 11 dkh
GH: unknown
pH: 7 (I think, based on colour of pH indicator)
NO3: >40 mg/l
PO4: >2 mg/l
Lights: 110 W for 10 hours

My tank is about 100 litres (~25 gallons). 2.5 ft Juwel tank.

My bioload is >80 fish (ok, sounds like a lot, mostly small tetras and corys).

I feed TetraBits once or twice a day.

Fertilisation: Seachem potassium 2 mg/l per week. TMG 5mg/l per week.

What is the most likely source of high NO3 and PO4? I suspect it's my high bioload and fish food. If so, should I feed less or reduce bioload?
----------------

Boon Yong, Are you adding any root tabs that contain N & P. IME, these are big contributors to the NO3 and PO4 level in the tank. I think with your high lighting, the plants should be able to handle N & P from the bioload.

----------------
Some advice I've received: add more K. Some nutrient is possibly missing and preventing uptake of N & P. Is this true? How about magnessium and sulphur? Do I need to dose these in higher quantities as well?
----------------

Yes. Keep up the K... about 20mg/L weekly. Look out for Mg and Ca deficiency. Rarely will you have S deficiency. You might want to consider Seachem Equilibrium. It provide K, Mg, Ca in good amount. I think you can increase your dosage of TMG to about 10ml to 100L.

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My main concern with the high NO3 and PO4 is the high level of spot algae I get. Other than these, I've no other types of algae. But the spot algae does attack and overwhelm my moss. To a lesser extent, my glosso is also attacked and if not for the fast rate of growth, I'm sure it'd be dead by now.
----------------

Monitor you PO4 and NO3. Do not allow any of it to fall too low. Keep up with K and traces(TMG). Keep up your CO2. Do weekly water change. You should be fine.

BC