Water Quality Whack-a-Mole

must manage the whole megillah

Wed Nov 16 2022


This extract is pulled from the WQ ToolBox manual, a companion of the Water Quality Map software.

The manual aims to bridge the gap between (1) overly simple explanations of water quality that don’t adequately inform aquaculture management practices and (2) important results in the research literature that are not readily accessible without a firm tech background.

It does that by helping aquaculturists build a strong foundation of basic water-quality concepts and essential tech vocabulary, the better to interact more effectively with colleagues and tech specialists.

This document was developed with Idyll [1], a “toolkit for creating data-driven stories and explorable explanations”. Custom components were built with React and D3.

contact aquacalc@protonmail.ch

A Balancing Act

The example below illustrates some of the challenges involved in managing water quality in even a very simple system.

If too much attention is placed on solving one problem, that solution may cause a different problem to pop up.

And if you then turn your focus to solving that new problem, then another problem -- a different one, or maybe the original problem -- may have to be whacked down.

You end up playing Water Quality Whack-a-Mole. Not ideal for a crop that would grow best in a balanced culture environment.

Our Example

Our problem centers on pH, a core water-quality property.

It can be challenging to find the pH range that satisfies the criteria of all important water-quality properties.

  • When pH is high, CO2 and Ω (carbonate saturation) levels may be safe, but UIA-N may be a problem and hydroponic plants may be unable to absorb essential minerals.
  • But when pH is low enough for safe UIA-N, then CO2 may be dangerously high, Ω too low to form strong carapaces and shells, and nitrifying bacteria may have sub-optimal conditions to function efficiently.

Playing with the interactive display below will give you a “feel” for this aspect of pH management.

Water Quality Whack-a-Mole

The game: adjust pH so that all water-quality properties fall within their safe range (i.e., each light is either green or yellow). Your targets:

  • Carbon dioxide (CO2) should be less than 10 mg/L
  • Un-Ionized Ammonia-Nitrogen (UIA-N) should be less than 12.5 μg/L
  • Aragonite saturation (Ωar) should be 1.0 or higher

Start with a low pH, observe the effects, and then set a high pH to see the change.

Play with pH to find an optimum. How wide (or narrow) is that optimal pH range?

After you’ve found an optimum pH, change Total Ammonia-Nitrogen (TA-N) to see how that upsets the balance (it changes UIA-N); then search for a new optimum pH range.

[Simplifications: temperature (25° C or 77° F), salinity (30‰), alkalinity (2.5 meq/kg or ~125 ppm), & calcium (412 ppm) all are constant. No biogeochem processes are acting to throw you a curveball.]

pH 7.10 (NBS Scale)
TA-N 0.50 (mg/L)

The Take-away: If there is a pH optimum -- under some conditions, there isn’t -- it’s not always easy to find and maintain in a real-world setting. (And the optimal range may be very narrow, spanning only a few tenths of a pH unit.)

Trial-and-error, as in this demo, is an inefficient management approach: you smack down one problem...and another problem pops up somewhere else -- kind of like playing “Water Quality Whack-a-Mole”.

So, the goal is to identify the conditions under which water quality is optimal for your species, and then adjust the culture environment accordingly.

The Water Quality Map is designed to simplify that key task, alleviating the time and mistakes of a trial-and-error approach.


  1. Idyll: A Markup Language for Authoring and Publishing Interactive Articles on the Web, Matthew Conlen and Jeffrey Heer. Seattle, WA. 2018.