Aquarium Water Parameters

Introduction

Please note that this page is related to my own fish tanks and has been created as an aide memoire purely for myself.

Tap Water Baseline

This is usually rested overnight and maintained at a temperature a couple of degrees below the target tank temperature.

Temp: 23C

TDS: 7

pH: 6.2

KH: 0

GH: 0

NH3: 0

NO2: 0

NO3: 0

As can be appreciated by the above characteristics, the water from my tap is almost akin to RO water. Thus, to make it suitable for the fish that I keep, this water does need to be amended. The main focus points are general hardness (GH), carbonate hardness (KH) and other trace elements to aid plant growth.

General Hardness (GH)

Product: Salty Shrimp GH+

GH is a measure of the total concentration of dissolved calcium and magnesium ions in the water column. The reasons for ensuring they are present are:

  • Essential Minerals for Physiology
    The calcium and magnesium help fish with osmoregulation (balancing water and salt in their bodies), support heart and nerve function, and build healthy bones and scales
  • Support for Shrimp and Snails
    Invertebrates like cherry shrimp and snails require dissolved calcium in the water to properly form and maintain their shells and exoskeletons. A range of 5 to 8 dGH is ideal for them
  • Nutrient Uptake for Plants
    The calcium and magnesium help aquatic plants build strong cell walls and activate chlorophyll for photosynthesis. A 5 dGH level gives planted tanks enough minerals for proper nutrient transport without making the water overly hard.

Carbonate Hardness (KH)

Product: Arka KH Booster

KH is a measure of the total concentration of dissolved carbonate and bicarbonate ions in the water column.

In using Fluval Stratum as part of the tank’s substrate I fell into the Stratum trap. Because Fluval Stratum is an active, buffering substrate, its main job is to actively absorb carbonate hardness (KH) from the water to lock the pH at an acidic level (typically around 6.5). If you have hard water, this is a good thing. However, if like me, you have very soft water this is a bad thing because Stratum’s fondness to absorb KH meant that I could not raise the KH. This in turn prevented me from keeping Neocardina shrimp in my tank

As the Stratum ages, its ability to fight KH dosing will diminish and it is already showing signs of doing so. This leads to an inherent danger that the pH of the tank could swing wildly in the usual diurnal ph shift e.g. at night as carbon dioxide rises the pH could fall dramatically and make the water very acid. Thus KH dosing takes place to address this issue.

Fertiliser

Product: Tropica Premium Nutrition

To aid the growth of plants, post water change, I also add the appropriate amount of plant fertiliser each week to ensure trace elements for healthy plants exist.

Oase Styleline 175

This is my main tank and is based on an Amazonian biotope. Ahem, apart from Amano shrimp in the clean up crew (CUC)!

Common NameScientific NameNumber
Rummy nose TetraPetitella rhodostoma10
Green Neon TetraParacheirodon simulans6
Lemon TetraHyphessobrycon pulchripinnis10
Splash TetraCopella arnoldi9
Duplicate CoryHoplisoma duplicareum5
Adolfo’s CoryHoplisoma adolfoi6
OtocinlusOtocinclus5
Amano shrimpCaridina multidentata10
Stocking List

Water Parameters

Temp: 25C

TDS: ~130

pH: 6.4-6.8

KH:<1

GH: 4-6

NH3:0

NO2:0

NO3:<10

Dosing

General Hardness (GH)3.5 grams
Carbonate Hardness (KH)3.4 grams
Fertiliser8 squirts

Superfish Scaper 60

Presently, this tank is used as a quarantine tank for any new additions to the main tank. Not that it looks like a typical quarantine tank(!), because I couldn’t help but ‘scape it a bit, which subsequently makes extraction of fish from here to the main tank a tad difficult. Lesson: Don’t ‘scape a quarantine tank…

With the main tank nearing capacity, the future plans for this tank will be to hold SE Asian fish, such as Harlequin Rasbora.

Water Parameters

Temp: 25C

TDS: ~130

pH: 6.4-6.8

KH:<1

GH: 4-6

NH3:0

NO2:0

NO3:<10

Dosing

Obviously, I use the same products for this tank as I do for the main tank. The differences come in terms of lower dosages for a smaller tank.

General Hardness (GH)2.5 grams
Carbonate Hardness (KH)2.4 grams
Fertiliser3 squirts

The Nitrogen Cycle

When you purchase a new aquarium you can not immediately put fish into it. To do so will induce a protracted and cruel death for any livestock.

Instead, you have to cycle your tank, which involves ensuring your aquarium is full of beneficial bacteria (Nitrosomonas) which can break down ammonia/NH3 (generated by fish poo, uneaten food and other detritus) into nitrite/NO2.

Subsequently, other beneficial bacteria (Nitrobacter) can break nitrite down to nitrate/NO3, which isn’t as toxic to fish as the previous two chemicals and can be taken up by plants.

This near-virtuous circle (you’ll probably still have to do water changes to dilute the nitrate build-up) is known as the nitrogen cycle. But to get it up and running takes some patience – up to a month.

I use an aquarium test kit to track the water parameters of my aquarium. The test kit is from NT Labs and it tests for the aforementioned chemicals that make up the nitrogen cycle (ammonia/NH3 > nitrite/NO2 > nitrate/NO3) as well as pH (acidic to alkaline), Carbonate Hardness/KH, and General Hardness/GH.

Living in Glasgow, Scotland means my tap water is very, very soft, with near zero KH and GH. Thus, to provide some buffering in pH swings, I have to add a KH booster (from Arka), and do so up to a value of 3 or 4. For GH I use Seachem Equilibrium

Below you can see a graph of these water parameters, and from mid-October 2025 through to November you can see the nitrogen cycle running its course.

Imbed with custom width & height + Scrolling enabled

Links

The (almost) Complete Guide and FAQ to Fishless Cycling