PH & Carbonate Hardness (KH)


Got Buffer?

Two of the most under-tested and maintained parameters in an aquarium system are pH and KH! Hydrogen potential and carbonate hardness respectively. I would lump nitrates in that group but many are aware that is an important chemistry and is frequently tested for. This short article will give you a little food for thought when attempting to solve some chronic problems or perfect your aquarium.

PH fluctuates considerably mainly because of the biological/physiological parameters in your aquarium. The goal is to keep your pH from fluctuating during a normal diurnal (24 hr) cycle by maintaining a refugium, buffering with supplements, or both. By raising the alkalinity, or buffering capacity, and/or reducing the effect of CO2 on your system you can defend against these fluctuations. A refugium is basically a secondary aquarium with massive macro-algae growth that functions under low lighting when your main aquarium is “sleeping” (i.e. main lights are off). Why a macro-algae garden you ask? I’ll answer with a question. What do fish breathe and what do plants breathe? Fish breathe O2 and “exhale” CO2, plants – or algae in this case, the only true saltwater plant is the mangrove tree – “breathe” CO2 and “exhale” O2. Now think about what happens when the lights go out in the main aquarium. Live rock, coralline algae, and macro-algae all stop their photosynthesis (reduction of CO2 and production of O2) which drives the production of chlorophyll, a plant’s food source. Only problem with that is, the animals in the aquarium continue to “exhale” CO2 even when the lights are off which then starts to affect pH. CO2 acts like and acid and reduces pH – or the “hydrogen potential” – of an aquarium for however long the lights remain off. The concept of the refugium continues the CO2 reduction thereby keeping pH levels stable. With a good crop of macro-algae some systems may have no dips at all and keep a constant 8.2 pH.

Alkalinity buffers can and, in my opinion, should be used in all systems since it is an excellent guard against potential problems like, for example, the asexual flush of all chlorophyll that very rarely happens to crops of macro-algae. I’ve only seen this happen once in my years of aquarium care. It’s actually pretty amazing. Within seconds 15 to 20 pounds of macro-algae will turn an opaque tan color as it dumps all its chlorophyll and will turn an aquarium a bright green. If you have a good skimmer it takes around 2 hours for the green to be removed. In a case like this you no longer have a photosynthetic crop of algae to continue reducing CO2 at night. Buffers can guard against pH changes until more algae is acquired and a new crop is established.

Carbonate Hardness (KH) or “calcium carbonate concentration” is another water parameter that really needs close attention, especially in reef systems. Depending on the calcium demands of your aquarium, you may or may not have to add additional supplements to maintain calcium levels for good coralline algae or coral growth. Your stony corals are especially sensitive since they are perpetually “building” and low or neglected levels can actually cause a die-off. Make sure you use the appropriate liquid test kit to evaluate your calcium levels. If low, find a good calcium buffering system like Kent Marine’s Tectra Tech CB A & B solutions that are for both alkalinity and calcium maintenance.

Keep and eye on Nitrates, pH, and KH in your system as these three do affect each other directly. High nitrates can inhibit calcium uptake by your coralline algae and corals as can low pH. High levels of calcium can cause calcium precipitation (calcium “rain”) which can coat everything in your aquarium and make a huge mess all over your rock and corals. Remember to test, test, and test again! Don’t fall into the trap of thinking that your aquarium has been doing well for so long that you don’t really need to test anymore becomes your motto. I’ve seen many an aquarium-keeper cry because he did not nip a problem in the bud by keeping on top of his/her testing.

Water Testing



One of the most neglected aspects of aquarium care is water testing. Sooo many problems can be avoided by just keeping an eye on the water chemistry of your fresh or saltwater aquarium. AND, sooo much time and money can be saved as well.

If I had a nickel for every time someone tells me their freshwater aquarium, “has done well for years and I’ve never had to do a water change.” Eventually, and inevitably, these people learn the hard way about water testing. Typically their systems crash unexpectedly, mysteriously! SPEND TIME AND ATTENTION ON WHAT YOU CAN NOT SEE IN YOUR AQUARIUM, & LESS ON WHAT YOU CAN!

I look at my water testing as something to look forward to because I know I’ll discover one of two things; 1) The system is healthy, or 2) The system is showing signs of becoming unhealthy to the inhabitants. I NEVER test and find that the aquarium is unhealthy because of the simple fact that I test frequently (i.e. once a week, or for smaller aquariums, <55 gallon, twice a week – smaller volume aquariums can have changes in chemistry much faster than larger aquariums).

Don’t make the mistake of thinking that your aquarium has reached the point of perfection and will stay there. Aquariums are not perfect and will never be perfect. Mother nature throws curve ball after curve ball and you need to stay one step ahead or risk losing, in some cases, a huge investment.

My recommendations are to avoid any form of test strip, absolutely no quality control there, and historically unreliable when I’ve used them. Invest in a good liquid based “drop” test kit(s). My favorites are API (Aquarium Pharmaceutical Inc), or Red Sea. These are color comparison kits which react with the specified molecules (i.e. NO3, NO2, NH3, etc.) and give you an approximate amount or titrate to an end point also giving you and approximation. Sounds difficult but really is quite simple. READ THE INSTRUCTIONS CAREFULLY, otherwise you may skew your results.

FRESHWATER: The Big 3! Ammonia, Nitrite, Nitrate (Nitrates especially), pH, and GH

SALTWATER: The Big 3! Ammonia, Nitrite, Nitrate (Nitrates especially, much more problematic in saltwater systems!), pH (High Range), KH (alkalinity), and Calcium.

Don’t neglect your water temperatures, this is considered a very important water parameter! Fluctuations in water temps in a 24 hour period can wreak havoc on your animal health. One of the main reasons ICH will suddenly pop up in an aquarium!

In my 16 years of aquarium science immersion, I swear by testing!!

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