Articles by Randy Holmes-Farley

Salinity is one of the most important parameters measured in reef aquaria. It controls not only the salt balance between an organism and its surrounding environment, but also the levels of a host of ions in seawater that aquarists neither measure nor control independently. Consequently...

For many aquarists, pH is not something that they have much experience with aside from their aquarium. For many, pH is almost a black box measurement: something to be considered, but whose physical meaning makes little sense to them. This article will describe pH in an intuitive way (as...

Most reefkeepers know they need to measure alkalinity, and most know it has something to do with carbonate. But what is alkalinity exactly? Why is it important? How is it measured? This article will answer those questions and give you all of the information that you need to fully understand one...

The phosphorus atom is one of living matter’s basic building blocks. It is present in every living creature and in the water of every reef aquarium. Unfortunately, it is often present in excess in reef aquaria and that excess has the potential to cause at least two substantial problems for...

Introduction Nitrate is an ion that has long dogged aquarists. It is typically formed in aquaria through the digestion of foods, and in many aquaria it builds up and can be difficult to keep at natural levels. In the past, many aquarists performed water changes with nitrate reduction as one of...

There are many different ions in seawater, and as reef aquarists we generally only test for a small number of these. Calcium, magnesium, “alkalinity”, nitrate, phosphate, and ammonia, for example, are relatively easy for hobbyists to test at home using kits. Other ions, however, are more...

Alkalinity is one of the most important measurements that a reef aquarist can make. It can become rapidly depleted in many aquaria, requiring frequent measurement in order to maintain stable levels. While hobby test kits for alkalinity can be simple to use, some aquarists find them either...

There is no aspect of reef aquarium chemistry more important than calcium and alkalinity. Many of my previous articles have described various aspects of these systems in detail. In reading those articles, aquarists will note one pervasive theme: that maintaining appropriate levels of each are...

[note: edited on 5/29/2022 to update the nitrate and phosphate sections with higher recommended levels.] One of the main roles of an aquarist with a coral reef aquarium is to ensure that the conditions are right for their tank inhabitants. There are many different attributes of the aquarium...