High Phosphates ? How Is This Possible?

[30searay]

I set up my 110 gallon about a month ago. Planted about 60-70% of the substrate with various stem plants to get me going. Here are the tanks stats, they are a bit out of whack!

lighting: 330 watts (6x55)
CO2: pressurized; 1 bubble per second.
substrate: eco-complete (with laterite base)
filtration: external wet/dry bio filtration
pH: 6.6
kH: 9
gH: 15
nitrates: 20 ppm
phosphates : 10 ppm
ammonia: 0
nitrites : 0
feeding schedule: typical daily EI schedule using Greg Watson fert's.

Over the past week the pH hit the cut-off point on the pH controller and shut down the flow of CO2 to prevent a pH drop. However, pH just 'sits' at 6.6 so the flow of CO2 has never kicked back on. I know that based on the charts, the CO2 may be way over 30ppm but haven't figured out why the pH won't go back up even with a kH of 9 so I can adjust the Co2 downward. Shouldn't the high kH partially act as a buffer and raise pH? also, the phosphates are way out of whack. Not sure why... is it possible that the plants aren't growing fast enough and not absorbing the CO2 and nutrients? Any thoughts on this dilemma would be much appreciated.

 

[plantbrain]

Let me tell you a story about another Buckeye, as well as a group of them.
Matt thought he had 30ppm.
He kept adding CO2 until his plants looked good.
Fish where fine etc.
The pH/KH measurement suggested 220ppm of CO2.

Now he and I both knew that could not be possible and have live fish.

So was it the pH?
No, he used a calibrated pH probe.

So what about the KH?
Some places use PO4 in place of KH for various reasons in the tap.
Some for corrosion control, some for partial softening etc.

Non KH alkalinity can really through off your CO2 if you use the pH/KH chart.

You might consider a pH/CO2 drop checker method.
Or eyeball and keep a very close eye on the fish and progressively and slowly add more CO2 till you see good plant health/growth etc.

Make sure there's some decent water current and some surface movement.

Regards,
Tom Barr

 

[30searay]

Let me tell you a story about another Buckeye, as well as a group of them.
Matt thought he had 30ppm.
He kept adding CO2 until his plants looked good.
Fish where fine etc.
The pH/KH measurement suggested 220ppm of CO2.

Now he and I both knew that could not be possible and have live fish.

So was it the pH?
No, he used a calibrated pH probe.

So what about the KH?
Some places use PO4 in place of KH for various reasons in the tap.
Some for corrosion control, some for partial softening etc.

Non KH alkalinity can really through off your CO2 if you use the pH/KH chart.

You might consider a pH/CO2 drop checker method.
Or eyeball and keep a very close eye on the fish and progressively and slowly add more CO2 till you see good plant health/growth etc.

Make sure there's some decent water current and some surface movement.

Regards,
Tom Barr

OK - thanks Tom. The one thing I noted was that I tested all the water stats before setting the tank up and the tap water registered less than 1.0 in PO4. So, somewhere the PO4 spiked up from dosing. Also, if I keep adding Co2 won't the waters pH will drop down to around 6.0 (I also use a calibrated probe).

Thanks,
Don

 

[BHornsey]

Don,

What Tom's telling you is that the CO2 / kH tables work fine when carbonate is the only acid forming compound present. Unfortunately, a fish tank has many forms of acid, all driving down pH.

Investigate using a CO2 drop test (lots of references to it in this forum) and this will help you determine your CO2 level more accurately.

 

[Liam]

Usually wet/dry filters wouldnt be used on planted tanks, as they allow the Co2 to leave the water very easily. You could also leave out the water for 24 hours and then check your ph to see how much the Co2 is dropping the PH