Alkalinity is an important parameter in a planted tank because alkalinity directly sets the baseline pH of the water. Some plants and animals are sensitive to pH levels, for example because higher pH increases the possibility of ammonia toxicity. Getting a rough alkalinity measurement is reasonably straightforward and in addition to abundant aquarium hobby alkalinity […]
Read more →Category: Water chemistry
Science of water parameters: pH/KH/CO2 equilibria, measurement, buffering, interpretation.
Stable pH and transient pH changes To get started, let’s discuss factors that apply universally to planted tanks. For simplicity we’ll work under the assumption that aquarium hardscape and substrate is pH inert. Then there are two main ways pH can change, transiently, usually on a day/night driven cycle, and stably which operates more long-term. […]
Read more →I’ve been playing around with the relatively new Dust LLM (Gemini also helped a lot, GPT5 made code more robust) and decided to have it work through bicarbonate pH buffering in an aquarium. At equilibrium, the pH in an aquarium is determined by only two factors: the concentration of CO2 in the air over the […]
Read more →Despite all the advice to the contrary, I tried out some Caridina shrimp in the tapwater-based Shrimphaus. This did not go well and after 3 weeks there was only one brave survivor left. The usual way to keep soft water shrimp is to start with reverse-osmosis (RO) water which is selectively remineralised mostly to restore […]
Read more →An interesting and widely misunderstood concept is the distribution of carbonate species (DIC: dissolved inorganic carbon) in an aquarium. What you usually see is a form of Bjerrum plot where it looks very much like the amount of dissolved CO2 goes to zero as the pH gets much higher than 7. Where this goes wrong […]
Read more →Cambridgeshire has hard, alkaline tap water. A number of iron salts such as iron phosphates and hydroxides are essentially insoluble. This can potentially cause issues with lack of iron availability for plants in an aquarium. In both the Fireplace Aquarium and the Shrimphaus, modified estimative index fertilising provides plenty of phosphates, and the alkaline tap […]
Read more →In a high alkalinity low-tech (non-CO2 injected) aquarium like the Shrimphaus there is a significant amount of potential carbon dioxide locked away and mostly unusable by plants in the form of bicarbonate. High alkalinity also means high pH, both of which are reputedly bad for aquarium plants. In theory, you can solve both problems – […]
Read more →The carbonic acid / bicarbonate / carbonate buffering system is very important in an aquarium and largely controls both the pH and the resistance to change of the pH in the water. These three carbonate-based species can all interconvert in a connected equilibrium reaction: (1) H2CO3 (carbonic acid) ⇌ H+ + HCO3– (bicarbonate) ⇌ 2H+ […]
Read more →Absent active interventions such as injecting CO2 gas, having an ‘active substrate’ and the metabolic processes of fish and plants, the pH of an aquarium will equilibrate to a level mostly determined by the alkalinity of the water – the amount of externally supplied bicarbonate and carbonate ions. In most cases, “externally supplied” means came […]
Read more →NOTE: if you want to be really super-serious about measuring alkalinity you could consider instead the upgrade to this page: ‘Measuring low levels of alkalinity‘ The pH of water in an aquarium is a measurement of the concentration of hydronium ions H3O+ (or just H+ for short). Neutral water has a pH of 7, and […]
Read more →