Today I’m going to show you exactly how to take control of your tank’s water, reduce algae, boost your plant growth, and honestly… just give you a few less things to worry about—at least for your tanks.
I’ve worked with water parameters in one way or another for nearly 10 years — below is the knowledge and specific methods I regularly use to get optimal and safe parameters in my planted tanks.
Let’s dive in:
- Why do these parameters matter at all?
- The easiest way to measure
- water changes matter — a lot
- General Hardness (GH)
- Carbonate Hardness (KH)
- pH and a few myths
Why do these parameters matter at all?
Water parameters are important. More clearly put:
Water parameters will make or break your tank, hands down.
Other factors like CO2 usage and fertilization pale in comparison to the effect bad water parameters can have on your plant growth.
If your GH is low (or 0), you’ll have poor (or zero) plant growth, algae issues, and likely unhealthy livestock. Shrimp and other invertebrates will likely die in your tank.
If your KH is (unintentionally) sky-high, your livestock will also suffer, and plant growth will be significantly stunted and slow.
If your pH is outside the ‘standard’ 6.5−7.5 range, your plants will technically grow—but it’ll be slow, and likely stunted. Livestock will also suffer.
Hopefully that got your attention.
This stuff matters, not just for beautiful plant growth, but for proper care of livestock. Suffering is never a good thing for your fish.
The easiest way to measure
There are a few different methods to measure your water parameters.
Not all methods are equal. Test strips are extremely unreliable, and essentially unusable for those that aren’t able to easily differentiate between sometimes-slight color differences.
Reagent test kits are almost always the best choice for most aquascapers. There are digital meters available (I use Hanna meters), but the price is not beginner-friendly, and it’s important to know: you don’t need fancy testing methods to ‘get it right’.
For budget minded individuals, I’d recommend a proper reagent test kit—the API kits are plenty accurate for our needs as aquascapers:
Test Kits are a critical part of aquascaping. You need one — period.
There are numerous test kits on the market, each with slightly different methods of measurement. I’ve used this kit for nearly a decade, and it’s been as accurate as I’ve needed.Amazon
The Master Kit above is missing the GH and KH tests — you can buy them here.
You’ll need these two to get complete coverage of your water parameters. (These last a long time; you don’t need to test for this nearly as often, once you have a routine.)Amazon
Water Changes Matter — more than you think
Most people don’t consider how water changes affect your parameters beyond the usual “leave water out for 24 hours” (which is false), or “water change when needed” (which is also false, in most cases).
Water changes can mean the difference between “easy maintenance” and “nothing is ever stable” in your planted tank.
- 30% water changes, three times a week.
- RODI water if at all possible (it’s cheaper these days than it’s ever been)
- Agitate substrate and plant surfaces to remove organic waste
You’re probably thinking, “30% three times a week is INSANE”.
It’s not — you’re spending that time on something, whether it’s water changes, or purchases you make trying to figure out why your parameters aren’t right, or troubleshooting/testing to diagnose algae buildup issues.
Even if you ignore everything else in this article, remember this:
RODI water is the fastest way to a crystal-clear, headache-free tank.
This is without a doubt the MVP for any planted tank product I’ve purchased.
It’s cheap, it’s reliable, and it produces exactly 0 PPM water. Use RODI water, and you can “build” your water parameters from scratch. (You also eliminate a whole host of problems by starting with zero-PPM water.)Amazon
GH is an initialism (‘abbreviation’, essentially) of General Hardness. You might also see terms like ‘Total Hardness’, ‘ºGH’, or just ‘GH’. They all refer to the same thing: GH is a measurement of the calcium and magnesium present in your water.
When someone says “hard” or “soft” water, they’re referring to how much calcium and magnesium is present — the GH value.
Important:GHdoes not have to equal KH. In nature they’re often equal, but in our tanks these values can absolutely be different.
GH is essentially an “official” way to measure how much calcium and magnesium you have in your water, and you’ll want to know that — here’s why:
Calcium and magnesium are macro nutrients that are required for lush, optimal plant growth.
If your GH value is low, calcium and magnesium will be the limiting factor for plant growth in your tank, you’ll likely run into algae issues as you increase your light level and CO2. (More on that here.)
High GH/KH values are important for hardwater fish like certain Cichlids — and the reverse is true for discus, which thrive in softwater with lower GH/KH values.
Aim for a GH value of 4 – 7 in your planted tank. You’ll know if your tank is an exception to this range. (i.e. you’re doing a blackwater tank, or a discus biotope, for example.)
You’ll probably see the term “KH” in the aquarium world — that’s carbonate hardness. It’s a measure of the carbonates and bicarbonates in your water.
For our purposes as aquascapers, it has zero effect on most plants. Its sole purpose is stabilizing the pH value of your water.
For most aquariums, maintaining a KH of 3 is optimal.
Some tropical species of plants and livestock thrive in lower KH values, but these are exceptions to the above principle.
There’s one thing about KH I want you to remember:
KH changes can dramatically affect livestock.
Fish and shrimp maintain their cell structure through a process called osmoregulation, and sudden KH changes are extremely taxing to their health, whether KH is increasing or decreasing. As a result, I’d highly recommend testing your tap water (or RO water, if you’re able) to determine whether you need to modify your KH, and stick to it.
If you have livestock, proper care means ensuring your KH value is stable. Allowing this to significantly fluctuate is extremely stressful on fish and many invertebrates.
pH and the ‘swing’ myth
pH is essentially a measure of the hydrogen present in your water. It’s more complicated than that, but for our needs as aquascapers that’s enough.
Neutral water has a pH of 7, acidic water is lower than 7, basic water is higher than 7.
For aquascapers, a pH of 6.5−7.5 is the “ideal” range for nearly all livestock and plants. There are occasional exceptions on both sides (very-low / very-high pH biotopes, for example), but you’ll know if you have one of these exceptions.
You might see forum postings and articles online about reducing pH swing in your tank — within reason, this isn’t necessary.
Significant pH swings happen in nature, and are a natural part of the environment for nearly all freshwater livestock. If you’re curious, Dennis Wong has a great in-depth article on pH here where he goes into the details about what that looks like in various biotopes.
This parameter does matter, but don’t stress about anything less than a 1 – 2 pH swing over the course of a day.
What’s your experience with water parameters? Got a tip for changing water? Tell me in the comments!