• You are viewing the forum as a Guest, please login (you can use your Facebook, Twitter, Google or Microsoft account to login) or register using this link: Log in or Sign Up

Low Tech CO2 Considerations

Sorry to drudge up this old thread, but the info here is very interesting and comprehensive...

But I have a question along these lines regarding buffering substrates and how they effect kh in the low tech system... given that my aquasoil and clay substrate is meant to buffer, I do not add any bicarbonate to my change water, instead using only gh remineralised RO... my kh values are very low... usually no more than 1 or less...

Can I assume that the potential co2 concentration in my tank is severely limited because of the low kh values or does a buffering substrate effect this differently?

My shallow wide tank has a lot of surface aggitation... the coast to coast overflow and HOB planter boxes that spill water into it further the aggitation and the unsealed shallow wide sump also presents a lot of surface area for co2 gas exhange...

But I am seeing what looks like co2 related deficiencies in most of the fast growers despite a valiant attempt at good flow and distribution of the limited co2 I have... as Clive has said many times, look there first especially with holes and deterioration in leaves, but the low tech system needs to be taken into consideration...

I am not seeing algae much at all yet, but deficiencies are the first step to disaster...
 
Hi all,
hitmanx said:
Can I assume that the potential co2 concentration in my tank is severely limited because of the low kh values or does a buffering substrate effect this differently?
Click to expand...
Whatever the dKH is it doesn't effect the amount of Dissolved Inorganic Carbon (DIC) in the tank, that is set by the CO2 ~ HCO3- ~ pH equilibrium and relates to the 400ppm CO2 in the atmosphere.

All that changes is <"the form the DIC is in"> (dependent upon pH).

cheers Darrel
 
hitmanx said:
remineralised RO
Click to expand...

Is it possible to check the water in the tank. CO2 will only dissolve in water to a limited extent no matter how well the water is agitated an equilibrium is reached. If your tank water is very low TDS then plants will struggle to grow. Without bicarbonates you plants might be extracting dissolved free CO2 faster than it can dissolve back into the water. With bicarbonates most plants can extract CO2 from the bicarbonate ions and form carbonate ions which will cause the pH to rise. This is usually countered with weekly large water changes. Have you considered mixing straight RO water with tap water to give a total hardness of say 50 ppm (soft water) or more tap water to give a harder water. Or use rain water and tap water to the same effect but at less cost. Tap water also contains nitrates, phosphates and some iron, all of which are needed for plant growth.

Low cost TDS and pH pen type meters can be obtained from ebay and could be of use. However, both will give unreliable results with water with a very low mineral content ie RO water and rain water. But comparisons between tank and tap water could be informative. Your water supply company should publish the water analysis for your tap water.
 
Oldguy said:
Is it possible to check the water in the tank.
Click to expand...

When filled in 2017 the water was 50/50 tap and RO so the gh and kh was about 12dgh/12dkh... that year I did only top ups with store bought RO, with no water changes...

In 2018 I started using homemade RO and 5 to 10% weekly water changes with salty shrimp remineralised RO to about 6dgh or 200ppm... the tank has hovered around 300-400ppm using my tds pen...

Last I looked ph was 7, gh was 10 and kh was 1 and tds was 295...

I will taking some measurements again at different times of the day to glean some hard numbers...
 
hitmanx said:
Last I looked ph was 7, gh was 10 and kh was 1 and tds was 295
Click to expand...

TDS does not appear to be a problem. It could be that your plants are removing CO2 faster than it can be absorbed from the atmosphere. CO2 is soluble in water compared to other gases but it is only slowly absorbed. All your plant growth: sugars, starches and cellulose came from the CO2 dissolved in the tank water.

Will be interesting when you have more data. Unfortunately I know nothing about 'salty shrimp'.

If you had good plant growth when the tank was first set up you could consider going back to 50:50 RO/Tap water but with much larger weekly water changes. What are your micro nutrients like. I ran low tech for years but always added chelated iron and additional potassium. I found obligate aquatics did OK with 10% water changes but emergent plants grown submerged started to become brittle and fall apart. However when 'rested' and grown in soil in a damp atmosphere, cutting became good to go for the next year. I think this was all down to CO2.
 
I tend to disagree with something here. For some people low tech = low light, and i tend to disagree with that. Although it is clearly quite difficult to keep a medium/high light tank without co2 injection, i have seen over the years on the internet plenty of examples of people who were successfull doing this.

As for myself have kept what i think is a medium lit tank without co2 injection for 14 months, without major issues and with minimal effort. You have to be careful what species of plants you keep and you must limit the number of different species in the tank, because they compete each other for the limited co2. It is difficult, but difficult does not mean impossible.

Michel.
 
You must log in or register to reply here.
Back
Top