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relationship between hardness and ph drop

papa_c

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Joined
22 Jan 2013
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368
A bit of background about the tank, 200l, CO2 injection, heavily planted, couple of Krebs, shoal of cardinal tetras, and oto's, water changes are from an HMA filter 50% weekly, gas on at 12.00 lights on at 4.00 till 10

My ph profile starts at 7.2 and drops over the 4 hours pre lights on to 6.8, drop checker is light green at lights on, if I increase the CO2 injection the fish suffer and all hang at the surface. This gives me the impression that CO2 saturation is quite high.

Based on this I would expect the ph to drop more than half a point. Checking the hardness of the water it is 465ppm

So is it the hardness of the water that is buffering the ph drop?
 
Checking the hardness of the water it is 465ppm
pH drop has less to do with hardness and everything to do with alkalinity (although waters having high GH usually also have high alkalinity. Is this measured value the GH or the alkalinity?

It shouldn't require 4 hours to drop the pH to the target value, so you should question the gas dissolution technique as well as the flow/distribution.

Cheers,
 
Edvet, plants growth is good in general, buy I suffer with loss of lower leaves on some plants such pogostomen erectus, but upper growth is good. However lower plants like dwarf eleocharis are doing fine.

Clive, the 465 ppm is a measure of TDS from a Hanna pen meter. Gas dissolution is via two in line diffusers giving even spread of micro bubbles across the tank, with two independent spray bars across the back of the tank from two separate external filters. Flow of the micro bubbles can be followed round the tank. The filters are Eheim 2215, so total lph is stated in total as 1200 but reality is a little less.

l have started to get BBA in some areas strangely in open areas.
 
the 465 ppm is a measure of TDS from a Hanna pen meter.
Well then this tells you nothing about CO2 or alkalinity.


l have started to get BBA...
I suffer with loss of lower leaves on some plants
This tell you a lot about CO2.

You need to know what the KH is in order to determine what your target pH drop should be.
Whenever the plants suffer CO2 deficiency at the same time that adding more CO2 stresses the fish then this tells you that either flow rate, distribution or dissolution are suspect.

Having two 1200LPH rated filters should be sufficient on a 200L tank so that eliminates flow rate as a potential problem unless there is a problem with tube/connector diameter, tube kinking or with excessive quantity of media. We would need to see how the filter outlets are arranged in order to analyze further.

If the BBA tufts are only on hardscape then this is not too much of a problem, but if it is on the plants then this is a big problem.

Cheers,
 
Hey Clive,

I've caused a slight confusion on the filters, I have 2x600 giving a total of 1200lph. Filter media is course sponges and a litre of siporax in each on top of the sponges.

Here is an image of the tank, you still be able to make out the position of the spray bars.

5PeYWS.jpg


Closer image of the BBA, you can see a little BBA growth on older leaves as seen behind the wood.

ZJGavC.jpg


I have a water report which had no mention of kH, so I have used the dreaded LFS bought test kit for kH measure, given all the posting on test kits reliability, in your opinion is this suffice?

kH shows 170
gH shows 220

It's maintenance day today, so I'm looking to prune out the older leaves affected with BBA.

I'm open to suggestions and advice so fire away!
 
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slight confusion on the filters, I have 2x600 giving a total of 1200lph.
OK, well, as you know, the 10X rule is the rule of thumb and you haven't met it. When the plant mass is low you can usually get away with it, but as the mass increases you tend to NOT get away with it, especially if the light intensity is high.


kH shows 170
So that's about 10 dKH which is medium, so a 1 pH unit drop ought to be the target and is not out of the question. As I mentioned before, if it takes 4 hours to drop the pH by 1/2 unit then that usually points to flow/distribution issues.

The crypts look as if they might be blocking flow across to the rear so it will help to trim them back.
You may want to think about daily supplementing with Excel or equivalent, which becomes expensive on that size tank.
A powerhead or couple of nano powerheads mounted just below each of the bars will help if you don't want to invest in more muscular filters.
As always light intensity is the main driver, so reducing it will help.

When you do a water change, drop the water level to below the horizontal section of the wood and use a small paint brush or eye dropper to nuke the tufts with Excel/equivalent. That only cures the symptoms of course.

Cheers,
 
Subscribed. I've often wondered what the consequences are (if any) of using water with very high tds.

Eyebrow tweezers can be used to pull of most the bba,. As mentioned above, lowering the water line and exposing the bba infected dw is a good idea. Leave it soaking in Excel or 3%-6% hydrogen peroxide for at least 10mins with the filter off and lights on.
 
Hey Clive,

update on this, looking at all the co2 related posts my belief is that my problems will never really go away with such a small filter flow, so I have taken the plunge and upgrade the files to 2 x 1400 lph so this should now give me over 10x turnover.

I moved the filter media from my old eheims to the new filters, set up switched on and the flow is amazing. Coming back from work tonight the water is now cloudy, almost as though a litre of milk had been poured in there, it wasn't like this this morning, any ideas what it could be? The tank was running for 24 hours before this happened.

Could the flow be too for the amount of media to have any biological effect on the water, One of the media trays in each of the filters is empty to try and machine flow.
 
Hi mate,
It's difficult to say exactly. It could easily be that the stronger flow kicks up more debris and keeps the particles in suspension longer.
It could be a bacterial bloom due to higher oxygen/CO2/nutrient availability. I really wouldn't worry about it because it will clear eventually. Do more water changes if it annoys you.

Cheers,
 
Seems he's doing okay, not quite enough CO2, the plants are not covered at least in BBA, just wood and lack luster plant growth.

Use a pH meter and try the 1.0-1.2 pH drop if you leave the tank be without CO2 for a good 24 hours without lights etc.
Skim off any surface scum you can see before doing that.

the pH meter will come in handy in real time for years to come.
 
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