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I want to make sure everyone knows that the pH of your tap water immediately after you draw it from the pipes, may not be real pH of your tap water.

This is some info that I didn't originally know it is caused me all sorts of confusion. Water from the pipes or well is often depleted of O2 and full of CO2 the carbon dioxide in the water forms a weak acid which will give a lower pH to the water if measured right away. If you take that same water and let it air (run it through a system or put it in a bucket with a bubbler) to let the CO2 escape then test the pH again, the pH will often be much higher. Example, my well water comes out of the tap with a pH of about 7 usually and after outgasing, it will have a pH of about 8.

This is important to know when doing water changes in a system that is likely to settle with a much lower pH or if dealing with a system that is not fully cycled and you are having high ammonia since higher pH makes ammonia more dangerous to your fish.

It is also good to know this info about tap water when dealing with pH balancing issues. If you are trying to hold a pH around 7 and adding lots of tap water causes pH to go up, then you want to keep water changes and additions small so the system can bring the pH into line without lots of bouncing.

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Just so I understand correctly, the source of my water's lowered pH to 6 (normally 7.8, 7.2 with driftwood) is/could be due to overfeeding?
Well, lack of buffering is what lets the pH get too low, see the bacteria use carbon in their process so in a sense the feeding causes the pH to go down but it isn't necessary "overfeeding" unless the fish are not eating it all or if there are ammonia/nitrite readings.
Hmm.. Nope. They devour it all and I have no ammonia/nitrate readings. I've just been baffled about the possibility of "overfeeding" my fish ever since the guy at the fish store told me that feeding them twice a day was too much (though I never told him how much was in each feeding... A silver dollar's size for 12 3" - 8" fish doesn't seem "too much" to me), and the source of the acid.

So, I have two tanks, the 20 gallon and the 55 gallon. They both have the same tap water source. There is a driftwood that used to be in the 20 gallon and is now in the 55 gallon. In the 20 gallon with tap water and the driftwood, the pH was around 7.0. Without the driftwood it's a 7.8. Conferring with the local fish store literally down the street, this is typical for the area.

The 55 gallon with tapwater and the driftwood keeps dropping below 6.0 (my test only goes to 6.0, and pH Up brings it up only to 6.8, which promptly drops again after a week).

I'm sure the lower pH makes the plants happy, but I would bet it contributed to the death of my pleco (the replacement is more tolerant of pH, thankfully).

Any ideas?
To help keep the tank buffered, you might think about adding some shell grit. Shell grit is a buffer that will add calcium carbonate to the system. The shell grit will only dissolve when the pH drops below about 7.6 and provide the carbon that the bacteria needs and can help keep the pH from fluctuating too rapidly. Shell grit won't bring pH up quickly but it will help keep the pH from dropping once you get it where you want it.
A friend suggested an additive called Blackwater. Would this contain buffer, or do I need to get a more concentrated version?
Emma Lysyk said:
A friend suggested an additive called Blackwater. Would this contain buffer, or do I need to get a more concentrated version?

Emma, firstly let me ensure you that I realise that you run ornamental fish... as opposed to most in aquaponics that stock freshwater fish for eventual human consumption...

And to assure you that nothing personal is intended in any way...

And to declare quite clearly my almost universal to all aquaria based products... as most on other forums would no doubt be aware...

Why.... quite simply because most are poisonous and or carcenogenic... and extremely hazardous to human health...

To be specific about the "Blackwater" product you mention...

Firstly... No ... it does not contain any pH buffering agents what so ever...

Secondly, after a little research... frankly I think the manufacturer should be sued for complete mis-representation and mis-labelling....

The product description reads...

Blackwater Extract contains trace elements, vitamins and extract of peat. It replicates blackwater conditions by creating clear, “natural”, Amazon-biotope conditions in the aquarium. Blackwater Extract promotes fish activity levels and is an excellent conditioner for all soft-water fish including discus, angelfish, tetras and killifish.

http://www.tetra-fish.com/sites/tetrafish/catalog/productdetail.asp...

But once I found the MSDS... I found that the product actually contains NONE of these things... or at least NONE of them are the "principal" ingredients...

The "principle ingredient" is in fact a Class 1 poison... banned, or heavily restricted in aquaculture... with known human side affects and issues of "sensitisation".... which I wont bother to reference at this stage...unless people wish to know...

The principle ingredient is often used in aquaculture.. for disease control, principally for treatment of severe finrot and parasites like "ICH"... perhaps their justification for "happy, smiley fish"...

The MSDS... http://whatsinproducts.com/msds.php?brandId=7988&PHPSESSID=754a...

Clearly states the principle ingredient .... as Formaldehyde ... "Formalin" ...

And frankly, compared to the Australian MSDS for Formaldehyde/Formalin... is soooo understated and benign... as to be concerning...

For those that want to persue it further... try googling "formalin"... or "toxic affects of formalin".. etc, etc...

It is extremely scary stuff... albeit that this product might be susbstantially diluted...

In standard form... inhalation, particularly in asthmatics... can cause respitory collapse... and full, almost hazmat style suits are recommended... at least here in OZ...

IMO... other than perhaps for those stocking ornamentals... dont use it... in fact IMO... don't use any aquaria products in aquaponic systems which contain fish you intend to eat...
Thank you, Rupert, that's precisely what I was looking for. I want to use the same tank for edible fish and don't want to contaminate it, so I've been trying to keep that in consideration.
Hi Emma! I have the same thing going on with my pond and my 135 gallon tank. I have driftwood in the tank and none in the pond. Our tap water is very high in ph. But, in my tank it is right around 6.8-7.0 because of the driftwood. Back in the old days I raised wild Discus fish which are from the Amazon and they love low ph water so I had a back filter on my tank that I filled with Spagnum Peat Moss and would just keep packing it in as it rotted. It gave the tank a brownish tint, but lowered the ph. I am using the same concept in my pond here, because of our really high ph tap water. It is helping, but takes awhile to get the process started. If you think about it the Amazon has a lot of debris that falls into the water and rots such as trees and leaves. This creates much more acidic water. Guess we all have to be vigilant at finding what works best for what we are given!
Oh! The one it was is Kent Black Water Expert. Looking at it closer, I don't think adding more humic and tannic acids would help.
The drift wood or peat can help lower pH but they are not a "buffer." In an aquaponics system where you are not doing extensive or regular water changes, the action of the bio filter long term will bring system pH down over time if there is no buffer in it.
Very true- it's also good to remember that nutrient uptake by your plants can have an effect on pH, although it's usually drawn out over time, or limited to times where the system goes from unstocked with plants to highly stocked (i.e. batch planting- not ideal) depending on what your nutrient load/composition is, plants can impact your pH by selectively taking positively or negatively charged ions out of solution. . . not a huge impact compared to moss, biofilters, barley straw, bogs, etc. but definitely an impact. . . thought i'd throw that out there if we're trying to figure out all of the things that can throw your pH off. : )

TCLynx said:
The drift wood or peat can help lower pH but they are not a "buffer." In an aquaponics system where you are not doing extensive or regular water changes, the action of the bio filter long term will bring system pH down over time if there is no buffer in it.

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