KH falling

kcomersr

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Jun 7, 2015
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I use RO water--collected in a 32g plastic garbage can. Prior to posting this question, I tested my RO water and it is neutral in respect to PH, KH, and GH. Before doing a water change, I always carefully adjust the KH to 4dH using Seachem Alkaline Buffer and the GH to 4dH using Seachem AquaVitro Mineralize.


My aquarium is an ADA 120p. I use Aqua Soil. All my gear, plants, and hardscape are from Aqua Forest. My 50 tiny fish are from Albany Aquarium.


Two months ago, I remodeled the 2+ year old aquascape in my aquarium. I cleaned the tank and discarded the components of the old 'scape, except for one piece of driftwood. Otherwise, the substrate, hardscape, and plants are new. All has been going well.


Except: I can't seem to maintain the KH at 4dH. It quickly falls to 3dH--and may fall below that except I've been dosing with Alkaline Buffer to keep it up. Recent testing indicates that the drop occurs relatively quickly. Yesterday I added Alkaline Buffer directly to the aquarium to reset the KH to 4dH before the lights and CO2 came on (target ph=6.6). At the end of the photoperiod, the KH was again at 3dH. I'm using API test kits.


I've been researching what could cause this drop in KH. It's a good thing I don't have anything else to do.


Ammonia is 0, nitrites is 0, nitrates are -- currently -- somewhere around 10ppm. When I first began investigating this, nitrates were around 40ppm (I do weekly 50+% water changes). As this seemed high, I took a look at the piece of retained driftwood and discovered that it may have exceeded its useful life. 3 days ago, I removed it and did a 60% - 70% water change. Since then, the nitrates have remained low but KH is still unstable. I'm currently fertilizing using the EI-lite recipe for a 60 gallon (5/8 tsp KNO3; 5/32 tsp KH2PO4; 3/16 tsp Plantex; 3 x per week).


I've have cleaned my Eheim 2078 canister filter; replacing all pads and rinsing the media beds copiously with RO water. I added 300ml of Purigen for good measure.


Could I be experiencing residual effects of a rotting piece of driftwood? Does constant dosing of Alkaline Buffer gradually raise alkalinity/ph of the water? I'm out of ideas.
 

Marcel G

Banned
Jun 5, 2012
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Czech Republic
Alkalinity consists of [HCO3-] + 2[CO32-] + [b(OH)4-] + [OH-] + [siO(OH)3-] + [MgOH+] + [H2PO4-] + 2[HPO42-] + 3[PO43-] + [CH3COO-] - [H+].


So whatever deprives you of HCO3, CO3, B(OH)4, OH, SiO(OH)3, MGOH, xPO4, CH3COO ... or adds H+ into your tank, this decreases your alkalinity.


The main agents which do this are acids. Acids add H+ ions into your tank (for example, if you put HCl into your tank it dissolves into H+ and Cl- ions, and the H+ ions then bound to HCO3 or PO4 ions in the water, thus decreasing the alkalinity (or put in different way, the HCO3 and PO4 ions neutralize H+ ions by making a bond with them, thus "removing" them out of water).


So I would say that somewhere in your tank you have some source of acids (maybe a peat in the substrate) leaching into your water.
 

kcomersr

Subscriber
Jun 7, 2015
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Could the source of the acid be the decomposing driftwood? When I examined the wood closely, I discovered that much of the surface layer had softened. After pulling the wood out, this layer cracked and peeled to a a depth of 2 or 3 millimeters as it dried. I assume this indicates that the wood was decomposing and perhaps releasing humic acid. I hope so anyway.


Otherwise, the Aqua Soil would have to be contaminated as that and 3 rocks are the only other things in the tank--except for plants and fish.


Do you think it might be a good idea to run some carbon in addition to the purigen?
 

kcomersr

Subscriber
Jun 7, 2015
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The journey is the reward. And don't forget to read the fine print.


The idea that humic acids could be leaching from the aqua soil stimulated a new line of inquiry leading to this article from the ADA Aqua Journal: http://www.aquajournal.ro/static/www...001/index.html


Interesting quotes:

Lower pH and KH allow more free CO2 gas to stay in the water column and creates an environment in which aquatic plants can easily conduct photosynthesis with only a few exceptions.

As mentioned earlier, the humic acid contained abundantly in Amazonia tends to leach into the water if a high amount of alkaline substances such as carbonate is present in the water.

 


If the pH of tap water is about 7.5 and its KH is 2 to 3, a small amount of humic acid leaches out and stains the water slightly. If the pH and KH values of tap water are higher than these values, special care is required.


 


if you have high pH and KH in tap water, it's effective to use any Aqua Soil product along with a RO/DI water system.




So I've been shooting myself in the foot--again--by boosting the KH to 4dH.
 
Albany Aquarium? Albany New York? Have they opened again? They were a fixture on Everett Road forever, but I saw recently they were closed.

I use RO water.. but I still try to boost my GH to 4 and my KH to 1 to 1.5.... I just couldnt' get enough CO2 in the tank without the pH just diving... the stable KH really helps. I do 40% water changes twice a week.