New member, new journal, very low ph

[Sebebob]

Hi all,

Long time lurker, first time poster. Thanks for having me.

I started a tank about 1,5 weeks back. In, for me, completely new territory. Its a tank where im using only RODI water, remineralized with Apt sky(gh+). I decided to make a journal because I see a lot of conflicting information(or opinions?) about very low ph rodi tanks. And it now happens that this tank measures VERY low ph before co2 injection. Im not even sure if i can trust my ph pen(voltcraft pht-02 atc). It measures ph before co2 injection at 4.9(blue DC) and after 2 hrs of injection at a rate of 3bps(big bubbles) through a cerges style reactor it measures 4.6(almost yellow dc). So, journalling time. FOR SCIENCE!

Equipment used:

• Oase scaperline 60(60x35x35) 75L,
• Chihiros WRGB2 45,
• Oase Biomaster 250T,
• Nameless Co2 regulator,
• Throwaway bottles(gonna change to refillable next time bottle is empty),
• Cerges style reactor fed co2 through inline diffuser
• Glass lily pipes, skimmer filter inlet.

Tank decor:

• Black lava rock,
• Dark mangrove wood,
• Ada amazonia.

Plant list:

• Eleocharis mini,
• Bucephelandra kedagang,
• Rotala green
• Rotala blood red SG,
• Bacopa salzmanii purple,
• Myriophyllum guyana,
• Hemianthus glomeratus,
• Rotala sp. vietnam,
• Rotala ramosior florida,
• Ludwigia palustris super red
• Microsorum pteropus mini.

Tank has been dark started for about 4 weeks before adding all the tiny in vitro plants last week.

 

[Sebebob]

To sort of keep the timeline intact, lets pretend its next week(this week). Tank is running for almost 2 weeks. Plants are growing well, pearling starts 2 hr after lights on from the 3 least expected contenders; Rotala florida, the dwarf hairgrass and the java ferns. The rest follows later in the day. Even though they are still converting to submerged growth. Forgot to mention that the Amazonia is ver 1, but supplemented anyway with the sticks from ver 2. Overload? Maybe.

Im using gh plus at water change to remineralize to gh 6, leaving kh at 0. Aquasoil is gonna buffer kh anyway. Using 1 pump APT 3 per day.

Chihiros is currently set at R45/G35/B35. Plan is to work it up over a few weeks to at least 70% red, but that depends on how the tank evolves.

Ph is low, very low. I tried degassing a sample for 24 hrs, stirring occasionally, ph measured 5.2. In tank, just before lights on, ph measures 4.9(blue dc). Co2 peak, ph 4.6(almost yellow dc). As mentioned before, the color change in dc makes me doubt if i can trust my ph pen. Also, plants seem very happy so far, but its only been 2 weeks. Im hesitant to add more co2, so im gonna watch everything closely and leave co2 as is.

The pictures make the tank look more yellow than it really is. Tint in real life is a little cooler.

To be continued

 

[dw1305]

Hi all,
Welcome to UKAPS

Apt sky(gh+)

This one? <"2Hr Aquarist APT SKY">. It doesn't contain any carbonate salts (dKH), so won't add any carbonate buffering to raise pH. If you have <"alkaline tap water">? You can add a small volume of that to add dKH, or you could add potassium bicarbonate (KHCO3) Food grade is "E501".

I decided to make a journal because I see a lot of conflicting information(or opinions?) about very low ph rodi tanks. And it now happens that this tank measures VERY low ph before co2 injection

Have a look at @Roland's <"Soft water tank"> - <"pH problem in tank">.

cheers Darrel

 

[dw1305]

Hi all,

Im using gh plus at water change to remineralize to gh 6

You don't need to <"add that much dGH">. I have a cynical view that the aim of the sellers of these products is to part you from as much of your money as they can, and that nothing else matters to them.

You are going to add magnesium (Mg++) with your fertiliser addition, and you can add a minimal amount of calcium (Ca++) via <"calcium chloride (CaCl.nH2O)"> or calcium sulphate (CaSO4.2H2O).

cheers Darrel

 

[Sebebob]

Hi all,
Welcome to UKAPS

This one? <"2Hr Aquarist APT SKY">. It doesn't contain any carbonate salts (dKH), so won't add any carbonate buffering to raise pH. If you have <"alkaline tap water">? You can add a small volume of that to add dKH, or you could add potassium bicarbonate (KHCO3) Food grade is "E501".

Have a look at @Roland 's <"Soft water tank"> - <"pH problem in tank">.

cheers Darrel

Hi Darrel,

Thanks! Ive read many of your posts and im always impressed by used amount of hotlinks. Must be a lot of work, but very much appreciated 🙂 Im not adding any carbonate salts since the aquasoil is gonna buffer them to 0 anyway. Decided to try and see how a 0kh tank is gonna work out.

Thanks for the advise, but adding apt sky with weekly 30l water changes makes it last forever, so im not really worried about the cost. Im adding enough to reach a gh of 6 purely for the rotala florida. It has a reputation of being hard to grow well, so i challenged myself.

That said, i expected a larger ph drop through co2 injection because of the very low kh. Adding this amount of co2 in the tap water tanks i had before(kh6) made the ph drop more than 1.5 point.

Lots to learn for this experiment, looking forward to see how the tank matures.

 

[Andy Pierce]

You can trust your drop checker and probably also your pH pen. At very low alkalinity the usual relationship between a 10x CO2 increase relating to a 1x pH decrease breaks down and a smaller pH decrease represents a larger CO2 increase. I did some calculations that suggest at KH=0 and 30 ppm CO2 you'd have a pH of around 4.8, so pretty good agreement with you. Your non-injected pH of 5.2 is consistent with some reasonably feasible atmospheric concentrations of CO2 in your indoor setup. The ADA Amazonia does not "buffer KH" - it lowers KH, and yes, it is possible for KH to take negative values.

I'm with @dw1305 on the GH piece... going with Mg++ and Ca++ from the ferts is probably good enough for what you need for plants, although there might be a different answer if you want to keep shrimp.

 

[dw1305]

Hi all,

Ive ready many of your posts and im always impressed by used amount of hotlinks.

I know that everything <"you ever need"> is on UKAPS, so it just a matter of finding it.

That said, i expected a larger ph drop through co2 injection because of the very low kh

I'm not a CO2 user, but I think you just really need to use the <"colour of the drop checker"> to indicate your CO2 level - <"Buffering carbonates when dosing CO2">.

The advantage we have over most other forums is <"that we have members">, @Andy Pierce, @hax47 who understand the chemistry of dissolved CO2

cheers Darrel

 

[Sebebob]

Hi Andy,

That is super interesting, this is new information for me. I knew UKAPS was the place to be! Good to hear my ph values sound about right.

Can you please elaborate on the negative kh values? It was my understanding the aquasoil lowers kh to 0, but never heard of negatives in kh.

Ill leave gh as is because yes, i will be adding shrimp. I have a small 25l with about 100 bloody mary babies so they will soon need a space to live 🙂

Seb

 

[Andy Pierce]

Hi Andy,
Can you please elaborate on the negative kh values? It was my understanding the aquasoil lowers kh to 0, but never heard of negatives in kh.

The short(ish) answer is that KH is made up of both carbonate-based molecules and all acids so if you have no carbonate-based molecules you can keep lowering KH by adding more acid. Usually the 'and all acids' piece isn't important so gets ignored.

The longer answer is that KH is invariably measured as 'titratable alkalinity' which is how much strong acid (usually HCl) needs to be added to reduce the pH below some threshold value. This equation for KH is formally described like this: Alkalinity = [HCO3−] + 2x[CO3−2] + [OH−] − [H+]. [HCO3-] is the concentration of bicarbonate ion, and [CO3-2] is the concentration of carbonate ion. Under 'usual' KH conditions (which is not what you are doing with your 0 KH tank) the concentrations of both bicarbonate and carbonate are so much higher than the concentrations of hydroxide ion [OH-] and hydronium ion [H+] (this is the 'and all acids' piece) that you can for practical purposes ignore these non-carbonate-based components of alkalinity. In your case however, if you start off with no carbonates and define that as 0 dKH, then adding more acid, e.g. from the Amazonia, will further lower KH below the defined 0 point by contributing more [H+] and further reducing [OH-].

 

[Sebebob]

@Andy Pierce Thank you, for taking the time to write down this very clear explaination. Makes a lot of sense. Does this change anything specifically in this tank that I would need to keep an extra eye on?

@dw1305 mentioned salts to increase kh. Everything ive read so far basically advises against this, since it would just "wear out" the aquasoil faster. Would there be any advantage, or would it even be possible, to try and get my kh to about 1 with fresh aquasoil? Wouldnt the aquasoil simply lower the kh back to 0?

Again, thanks for taking the time to answer my questions. Much appreciated!

 

[dw1305]

Hi all,

mentioned salts to increase kh. Everything ive read so far basically advises against this, since it would just "wear out" the aquasoil faster.

Basically it will. These substrates work via "ion exchange" <"https://www.lenntech.com/Data-sheets/Ion-Exchange-for-Dummies-RH.pdf"> (ignore the title, this is a useful document), the initial cation is a proton (H+), bound to the exchange site on the substrate, and this will be exchanged for a cation of higher valency in the water column - <"Tropica Plant Growth Substrate Lifespan"> in <"the scenario"> from @Andy Pierce 's post.

Would there be any advantage, or would it even be possible, to try and get my kh to about 1 with fresh aquasoil?

Probably not.

Wouldnt the aquasoil simply lower the kh back to 0?

I think it will.

cheers Darrel

 

[dw1305]

Hi all,

I have a small 25l with about 100 bloody mary babies so they will soon need a space to live

They are better in harder, more alkaline water, but I don't whether dGH, or dKH, is the parameter that matters.

cheers Darrel