Question on Phosphates

[30searay]

I have a 110 gallon set up that is about 2 months old. I am still getting the hang of the fertilization schedule but for the most part the plants seem to be happy. It's my phosphates that seem to climb quickly and don't drop until the water change. the tank is well planted with val, cabomba, hygrophilia, various crypts, and anacarus (sp?). I am still experimenting with what grows best in the tank due to the depth (29 inches).

Here are the tank stats.

lighting: 330 watts 10 hours with 2 hour break mid-day
CO2: pressurized; 4-5 bubbles per second, about 28 ppm per the formula (I don't yet have a drop checker).
Substrate: eco-complete
pH; 6.8
kH: 9
gH: 15
Nitrates 15-20 ppm
phosphates 5 ppm
ammonia: nil
nitrites; nil

I am using the EI schedule while I determine the plants utilization rate of the ferts in the tank. Currently, I dose 1/4 teaspoon of the KH2PO4 on M-W-F along with the KN03. Traces are dosed on T-R-S.

What could be making the phosphates climb so high? It almost seems they are not being used by the plants. Algae is in check so far thanks to my friendly tank mates, although it is present in the tank.

 

[Jchillin]

My guess would be that your plant mass does not absorb an equal amount of the mono potassium phosphate that you are dosing. You could reduce the amount of KH2PO4 for a week and see if that helps.

 

[newfound77951]

I agree, I would just try tweaking the amount of P you add until you get the levels that you want. Maybe only add it once per week, or add it MWF but at a lower dose. I use the presence of green spot algae as my phosphate indicator....when it starts to show up, I need to add more!

 

[Purrbox]

It's possible that you are feeding foods that are high in phosphates. This would cause your phosphates to climb higher than expected.

 

[Plantbrain]

Tap water is also a possible added source, but..............before changing anything, are your plants fine?

Do you or anyone for that matter honestly believe and can rationally assume that there is a an algal, fish health or otherwise any issue between say 2ppm of PO4 and 5 ppm?

I challenge anyone to discuss a model or show evidence there is.

Issue no#2.
Test kits.
PO4 and NO3 test kits particularly.

Unless you calibrate them over the desired target ranges, they are no better than eyeballing based on a dosing calculator at best and at worst .........entirely wrong.

So..........unless those issues are addressed, it's not likely an issue.

Now let us assume that it is rising.[PO4]

Adding more CO2 generally will upregulate PO4 uptake by plants.
As well as NO3 and other nutrients.

330w is a lot of light for the tank, you or other folks may not think so, but I've set up a number of tanks this size for folks, try 220 w and see.
I bet the tank will do better and have less algae.

You can add more CO2, but not at the expense of fish, you can always add more CO2, do not reduce current to save a little CO2 while also reducing O2 exchange,. have good current and a little surface movement, not enough to break the water's surface, just below that though.

That will help fish health, allow more CO2 dosing wiggle room.
Rather than focusing on test kits for NO3/PO4, micro managing all that, try a focus on CO2.
You'll get a lot more success and results that way.

The premise for addign non limiting PO4/NO3/K/Traces etc is just that, to rule limiting nutrient levels, having a bit more is , well part of the obvious logic behind it.

Excess nutrients clearly are not algae inducing issues in our tanks, they have other factors, light and CO2, these are the main drivers, not some little nutrient like PO4.
You can test such things in a tank also to prove it to yourself.

Regards,
Tom Barr

 

[dapellegrini]

Joy is right that it could be your fish food. If you are using TAP water, unless you are constantly testing it, you may well get seasonal spikes there as Tom is alluding to. I dose way less PO4 than recommended in the standard EI routine as I seem to also have a high ambient level in my tank. Never tried to figure out why, just made a small adjustment to my routine.

I actually dosed PO4 heavily for a while on the (false) assumption that a low level was causing my problems with GSA. Ended up being too much light.

What I learned is that when my PO4 gets too high my fish start to swim funny. For instance my Rummynose would start to fall forward, going over 90-degrees nose first, before balancing themselves back out. Other fish started to swim a little lop-sided. Reducing the PO4 immediately remedied that problem. I cannot say with scientific certainty that PO4 was my only factor, but all indications seemed that way...

 

[30searay]

It's possible that you are feeding foods that are high in phosphates. This would cause your phosphates to climb higher than expected.

Purrbox: Thanks for the input. I try to keep the feeding simple. Only feed every 2 to 3 days - either flakes or brine shrimp. My tank friends consist of run of the mill community fish, swords, various tetras, corys, and goramis. Oh, and one puffer for snail patrol (he was necessary due to junk snail infestation from plant purchases). Also have 2 small ottos (tiny), 6 cherry shrimp, couple SAEs, and 2 plecos for clean up. Hope to get some angels over time as the existing habitants get used to their space.

I don't feed anything else to the fish.


quote="dapellegrini"]Joy is right that it could be your fish food. If you are using TAP water, unless you are constantly testing it, you may well get seasonal spikes there as Tom is alluding to. I dose way less PO4 than recommended in the standard EI routine as I seem to also have a high ambient level in my tank. Never tried to figure out why, just made a small adjustment to my routine.

I actually dosed PO4 heavily for a while on the (false) assumption that a low level was causing my problems with GSA. Ended up being too much light....[/quote]


Thanks - this is helpful. Both Tom and yourself allude to possibly having too much light? I am at 3.0 wpg with a very deep tank for a planted aquarium (29 inches). I would have to assume that I lose considerable light over this depth, no?

When I first tested the phosphate levels in the tank at original set-up, the test kit registered little, if any, PO4 in the water. So I commenced with the EI schedule and recommended dosage levels. I am struggling a bit with algae in the first month but currently appears to be in check. As of today, I don't notice any plant stress or unusual fish activity to indicate other issues. Plants appear to be pearling well and growing. I am going to lighten up on the phosphate dosage and dosing schedule and see what happens.

 

[Plantbrain]

I actually dosed PO4 heavily for a while on the (false) assumption that a low level was causing my problems with GSA. Ended up being too much light.

What I learned is that when my PO4 gets too high my fish start to swim funny. For instance my Rummynose would start to fall forward, going over 90-degrees nose first, before balancing themselves back out. Other fish started to swim a little lop-sided. Reducing the PO4 immediately remedied that problem. I cannot say with scientific certainty that PO4 was my only factor, but all indications seemed that way...

Dave, it's not your light, it's the CO2, I dose 2 ppm 3x a week with 300 Rummy noses, we have not restocked nor seen any decline in health in 3 years. Thus one may conclude that it cannot be due directly to KH2PO4 dosing.

There is also no research evidence of any sort that high levels, we are discussing here are bad for humans, fish or inverts, none.

I'm not saying what the issues are(well with the GSA I am), just what is cannot be due to based on using the same PO4 source and the same species of fish.

Reducing the lighting makes things a lot more manageable if you cannot address the higher/faster growth rates associated with high light though........that. rather than PO4 which can also increase CO2 uptake, can lead to algae and plant growth issues.

Limiting PO4 is not bad per se though.....plants respond better to limitation of PO4 than any other nutrients if you chose to limit things.

But we are trying to grow things faster when we add CO2 to begin with, so I just use light to manage growth and thus have a light limited tank, rather than CO2/PO4/NO3 limitations.

Regards,
Tom Barr

 

[Plantbrain]

The tank is 120 that was 24" depth, the 110 gal you have with these same lights will be fine as I mentioned to Dave's success, less light will make things more manageable.

220 w is plenty, this might seem like little... it's not.
Those lights are more intense than you think.

Some folks hee haw back and forth, but over time and when they get tired of fiddling, they generally end up seeing the wisdom of less light = more.

You are maximizing the light use efficiency use of the plants by adding CO2/nutrients.
So they grow faster when you add CO2/nutrients etc.

If you limit CO2, then adding more light will not help and allows algae to grow easier.
If you limit nutrients, same thing.

Both cases, you do not get the full use from the lights.
Light cost the most and things that go fast in aquariums are typically bad.

So slowing things down helps and while some do not mind daily trimming/work/dosing, most do after a little while.

Hortilculture has many goals and trade offs.
So there are many ways to achieve things.

We often assume there's a right way etc, that things are black and white, not, not even close.

The real issue is what trade offs best apply to our goals. Less light is perhaps one of the best.

Regards,
Tom Barr

 

[30searay]

Tom:

OK - so if I consider the reduction of wpg from 3.0 to 2.0 - which band of lights should be removed. The 5500k, the 6700k, or the 7800k? How do you determine how much to cut back on fertilization amounts with the reduced lighting?


Don