High pH and GH due to substrate...questions? - The Planted Tank Forum
 
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post #1 of 4 (permalink) Old 05-04-2015, 02:54 AM Thread Starter
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High pH and GH due to substrate...questions?

Folks:

Been a long time. Thought I'd run a scenario past you...

My 100 gal high tech planted tank was established in April of 2010. I have run pressurized CO2 since the beginning, having mixed success with several species. Within the past year, I changed over my moderate lighting (4x65w CFLs) to LEDS and I immediately saw an increase in growth, especially in my reddish colored plants.

I established this tank with the following mixed substrate:

EcoComplete (2 bags)
Seachem Fluorite (3 bags)
Pool filter sand (partial bag)
Zeosand (partial bag)
Hartz ph5 kitty litter (7 small "dollar" bags from dollar store)
Hyponex potting soil (partial bag)

All of this may, or may not have been a mistake. The partial bags were very much equal parts to everything else, so it was a very uniform mix.

My tap water (not changing much over the years) is pH 8.0, with 8kH and 11GH. TDS is approximately 160 ppm.

Running a drop checker and trying to keep my CO2 around 15 to 20ppm, I was able to keep the pH around 6.6 to 6.8. When my CO2 would run out, the pH would raise to 8.3.

Last year, once I added reef aquaria to my skill set, I invested in an RO/DI unit and I immediately started using 0 TDS water in my 100 gal tank. Over time, while using the same levels of CO2, my pH began to rise to 7.4/7.5. I was changing out water often at this point, and my TDS meter showed 300+ ppm after the first several water changes down to a current 250 ppm. Today, when measuring GH, I stopped putting drops into the API test tube at around 40 drops without it changing color.

Yesterday, when my CO2 ran out, my pH jumped up to 8.8.

I pulled out some substrate today and put RO/DI water in it...the pH measured 8.4.

It's obvious that the RO/DI water does not buffer like the tap water did, but I never used RO Right (actually I have Barr's Mix) because of the always high TDS even after the water changes. I was hoping and waiting for my pH and water hardness to naturally go down before I saw the need for adding the buffer.

I know that EcoComplete had a questionable reputation with regard to pH at that time, but you'd think it would wear off by now? Anything else that could explain it? Shouldn't the Kitty Litter be driving down the pH?

Anyway, I will likely redo the tank with a better substrate, like with dirt or aquasoil, but I thought I would ask here what you folks think is the dynamic I am seeing? I'd like to be able to grow some good plants!

I do not blame you if you TL;DR. My apologies!
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post #2 of 4 (permalink) Old 05-04-2015, 03:38 AM
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Originally Posted by jay52 View Post
Zeosand (partial bag)
I didn't know what Zeosand was so I Googled it. A lot of complaints about it from the pool crowed. Zeosand is a form of zeolites I took this from Wikipedia.

http://en.wikipedia.org/wiki/Zeolite

Quote:
Southern hemisphere zeolites are typically formed in freshwater and have a high calcium content.
A high calcium content could make your gH go up and thus pH.

Bump:
Quote:
Variations not only occur between different types of zeolites but also in the physical and chemical properties of zeolites of the same group. Source plays a large role in these variations. For instance, clinoptilolite from one source will not necessarily have the same properties as clinoptilolite from another distinct source. Environmental conditions during and following the geologic genesis of each source are rarely the same, causing these variations. The types and number of impurities present and the way in which the zeolites are cemented together are all dependent on the unique conditions during formation.
Finally, one difference between zeolites worth giving special mention is the composition of exchangeable cations residing in the zeolite. Exchange sites on natural zeolites are primarily occupied by 3 major cations: potassium (K), calcium (Ca), and sodium (Na) (other elements such as magnesium (Mg) may also be present). Exchange sites on a particular zeolite may contain nearly all K, nearly all Na, some Ca or Mg, or a combination of these. It is important to take these differences into account when assessing which zeolite to use for a particular product. Zeolites dominated by exchangeable K for example, may be well-suited for plant growth applications while those dominated by Na should be approached much more carefully as Na in high concentrations can be detrimental to plants
http://www.zeoponix.com/zeolite.htm


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post #3 of 4 (permalink) Old 05-04-2015, 03:55 AM Thread Starter
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Interesting thought. Thanks for the reply!

I know there was some reason why I used it at the time...knowledge of substrates has certainly improved in the past 5 years, so it might be the culprit indeed.

Just to add, this is a 3" to 4" substrate, never touched other than when planting. I wonder if thorough vacuuming might help? Perhaps a series of WCs where I spot vacuum small sections until complete?

Seems like changing substrates would be easier though. I have a big 100 gal Rubbermaid stock tank that can serve as a temporary home for the flora and fauna.
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post #4 of 4 (permalink) Old 05-04-2015, 04:01 AM
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Originally Posted by jay52 View Post

Seems like changing substrates would be easier though. .
I've not been real happy with the sub on my 40b for the last year. I've got what I need to change it out but the scope of the task and knowing just how much work it will be keeps me dragging my feet. But soon, very soon


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