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Active soil in an external filter ?


dao
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Hello,

 

I am running a planted taiwan bee tank on an inert substrate. To lower my pH I am using peat granulate by placing it in a mesh bag and inside the filter.

The result is quite good - I can get the pH down to pretty much any level I want, but stability is an issue. To have my pH in the slightly above 6.0 range which I want I need to add very small portion of the peat granulate (if I add more the pH can go down as low as ~5.4. obviously the reading might not be super accurate but in any case very low) and change it once every 3-4 days to keep the pH in a stable range.

 

So my question is: Would replacing the peat granulate and using an active soil of some kind would be a better idea ? And yes I mean placing the active soil in the filter, not restarting the tank.

 

The goal is to have a stable pH somewhere in the range of 6.0-6.5, but I am hoping that with an active soil the pH would go down just to a certain point, no matter how much I use it. If so, then I would be able to put more active soil than peat granulate at the moment, and as a result do less frequent changes with the buffering properties maintained.

 

What are  your thoughts on this ? Does this have any sense, and did anyone try this ?

If this is a valid solution what active soil would you recommend, and why?

 

Thanks

 

 

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Well since a lot of people (including me) use the soil as a substrate for the whole tank without the ph going too low I would say you wouldn't have to worry about that part, but I'm not sure if that amount you could fit in your filter would be enough to lower the ph by much.

Do you have something in your tank that would raise ph? Having it change it every 3-4 days seems a bit much to me.

Also, what kind of peat are you using?

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Thanks for your answer.

 

I'm using Sera Super Peat at the moment.

 

I'm not sure if there is anything that will raise the pH - I would assume no since there are no rocks and I have a piece of driftwood inside, but if I would use nothing to lower it , the tank naturally goes back to around +/- 7.0, which I assumed is natural as my second tank acts the same way.

 

As for the active soil - if you set up a tank you are using a lot more, but it lasts for a year or more - what I want to achieve is make it last just one week, since I'm doing water changes weekly.

When using peat the key was to provide good water flow around it, I assumed the same could work with the substrate.

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As for the active soil - if you set up a tank you are using a lot more, but it lasts for a year or more - what I want to achieve is make it last just one week, since I'm doing water changes weekly.

When using peat the key was to provide good water flow around it, I assumed the same could work with the substrate.

Why would you want to buffer for only a week? I use RODI water that lowers my 8.0 PH well water down to 6.2. I remineralize with SS GH+ and use controsoil to stabilze the water at 6.0-6.2. I do 20% water change once a week. The active soil is what keeps your water consistent and stable.

 You can get RODI units under $60,cheap simple and easy to use.

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Hm, are you using ro water? Mine will be about 7.4 ph if I don't add anything to lower it, so I guess milage varies.

I'm not sure if you could get enough substrate in the filter to lower it enough but if you did I would think it would last longer then a week.

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I guess the only way to know is to try it out. I was thinking about Akadama, as it is cheap and should be fit for purpose buffering to around 6.0-6.2.

 

@Vpier

 

I do use RO unit - my RO water is around 7.0. How come your RO water is 6.2 ? It would seem that there are some substances in the water that are lowering the pH, as it should be way closer to neutral pH.

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I guess the only way to know is to try it out. I was thinking about Akadama, as it is cheap and should be fit for purpose buffering to around 6.0-6.2.

 

@Vpier

 

I do use RO unit - my RO water is around 7.0. How come your RO water is 6.2 ? It would seem that there are some substances in the water that are lowering the pH, as it should be way closer to neutral pH.

My well water is very hard and contains large amount of iron, very typical in MN. I forgot to mention my well water goes through a softener first then my RO unit. Your question about why PH is lower for some and not others is not easy to answer but I found this on the internet that might explain better than what I can since I am not a chemist. Many people really don't pay attention to RO water's PH since its unstable until you add something to affect the chemical makeup of the water.

http://www.puretap.com/ph.htm

 

Below came from this source http://www.freedrinkingwater.com/water-education2/ro-ph.htm

 

This question is answered when you understand the equilibrium relationship between CO2, HCO3, and CO3. In a closed system, the relative amount of each dune compound varies with pH. At lower pH levels, CO2 is the predominant species. HCO3 is the predominant species at mid pH levels, and CO3 is present at higher pH levels.

Since RO membranes will reject dissolved ions but not dissolved gases, the RO permeate and RO feed will contain roughly the same amount of CO2. The HCO3 and CO3, however, are often reduced by 1-2 orders of magnitude. This upsets the CO2, HCO3, CO3equilibrium that was established in the feed. In a series of equilibrium reactions, CO2 will combine with H2O driving reactions similar to that shown below, until a new equilibrium Is established.

 

To summarize:

The new equilibrium will always result in a lowering of permeate pH if there is CO2 gas present in the feed water.

The pH drop is usually largest for waters with high amounts of alkalinity or HCO3.

When there is very little CO2, HCO3, or CO3, there is a very small pH drop observed in the permeate.

Therefore it is not true that reverse osmosis filters will always reduce the pH level of water to a noticeable amount. The pH difference after the RO depends on the composition of your input water source; depending on whether you have large amounts of gases such as CO2 in your local water supply.

 

My simple understanding is RO water has none or very little buffering capabilities thus making the water unstable so it takes very little to achieve the PH you need the water to be at. Using remineralizer for specific water conditions like SS GH+ and active substrate like ADA,Controsoil and Akadama will lower PH and keeps it at that level as long as your substrate has not been depleted.

 

Example, I have two storage tanks. One tank is for caridina and one is for neo's.

Caridina tank gets RO  and remineralize with SS GH+ and PH is around 6.2 on occasion 6.4. but controsoil keeps the PH around 6.0-6.2.

Neo tank gets the same RO water but I use SS GH/KH+ giving me a PH around 6.8,  so in that storage tank I use aragronite in large media bags and this buffers my water after a couple of days to 7.0.  Once I use up my SS GH/KH+ Im switching to SS Sulawesi 7.5 hoping this will keep my PH between 7-7.5 and I wont need the aragonite.

 I used to use Seachem buffers like discus buffer 5.8 and neutral regulator 7.0 but stopped because they use phospahtes.

 

Water chemistry has always been a complicated and highly debated topic.

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