Aquarium Test Kits

Updated August 12, 2019
Author: Mike - FishLore Admin
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An aquarium water test kit is needed if you want to be successful in the tropical fish hobby (freshwater or saltwater). You will need to know how to test your water during new tank start-up (the cycle) and whenever problems arise.

Aquarium Test Kit

There are many tests that you can use on your aquarium including:

Buying these aquarium tests individually can get expensive. You can usually save a few dollars by getting a master test kit. For most hobbyists these master kits will be sufficient. Live plant keepers and saltwater reef tank keepers may need to invest in additional specialized mini tests such as copper, phosphate, dissolved oxygen, etc.

Some aquarium water tests come as dip strips that you dip in a test tube filled with water from your tank. You then compare the color with the card that came with the kit to get your final reading for each particular test. The other type of test has liquid droppers. You dispense the liquid (certain number of drops) into a test tube with tank water. You usually need to shake the tube and wait a few minutes for the test to develop. You then match the color of the water in the test tube against a card to get your final reading. It can be a good idea to ask someone else in your house to compare the colors and give you a second opinion. Don't tell them what it means, just ask them to match up the colors. As hobbyists, we may tend to skew the results in our favor, so a second opinion may help keep us honest.

The Freshwater Master Aquarium Kit usually contain tests for ammonia, nitrite, nitrate and pH. Saltwater Liquid Master Kit usually contain tests for ammonia, nitrite, nitrate, pH and sometimes alkalinity. The Reef Master Kit has even more tests than the saltwater master test kit. See below for more information on these terms.

Aquarium Test Kits

The alkalinity test determines how stable your tank water is relative to a shifting pH. It can be thought of as your tank's buffering capacity or it's ability to keep the pH level stable. In most saltwater tanks you want this reading to be in the 7-12 dkH range.

This chemical is the result of fish waste and decomposing food in the aquarium. Ammonia is the leading killer of tropical fish. You want this reading with your ammonia test to be 0. Read about the Nitrogen Cycle.

Primarily for saltwater aquariums, a Calcium test is important to use when dosing calcium in reef tanks. Calcium is a primary element that corals need to grow and dosing calcium may be a necessity for the health of these animals. You need a test kit to determine how much and how often to dose. For more information on dosing calcium, please read Saltwater Supplements.

Chloramine is a combination of chlorine and ammonia. It is a stronger disinfectant than chlorine alone and is used in areas where this extra disinfectant is needed. As with chlorine, you must eliminate this chemical from your tap water before adding it to your aquarium or it too will kill your tropical fish.

This chemical is found in most tap water and it is used to kill the bad bacteria in our drinking water. Clorine must be eliminated before entering your aquarium or it will kill your tropical fish. You will usually only test once or twice for chlorine with your chlorine test just to see if you have it in your water.

This heavy metal can come in with the tap water if you have older copper pipes. It can also get introduced to your tank if you've used any copper based medications. Copper can be very harmful, even lethal, to fish and invertebrates so it can be good to have a copper test on hand.

An iodine test is needed for saltwater hobbists that keep corals or invertebrates that require iodine. Iodine is used up quickly by the aquarium inhabitants and skimmed out with the protein skimmer. I wouldn't recommend dosing iodine without being able to test it.

Another important parameter to keep an eye on for saltwater fish keepers is magnesium. You want to keep this in the range of natural saltwater which is 1200 to 1400 ppm. I try to keep mine in the middle around 1300 ppm. Magnesium is depleted over time and will need to be replace through water changes and maybe even dosing, but not until you get a magnesium test for it.

Nitrites are converted to nitrates during the cycling process. Nitrates are not as toxic as ammonia or nitrites but they are harmful and will stress your fish at high enough levels. You need a nitrate test. The only way to remove the nitrates is through a partial water change. Ideally you want this reading to be less than 20 ppm, in reef tanks you want this to be as close to 0 as possible. Read about the Nitrogen Cycle.

Ammonia gets converted to nitrite by the bacteria in your tank. Nitrite levels will soar in new tanks that have not yet been cycled. Nitrite is just as toxic to tropical fish as ammonia and the only way to quickly reduce nitrite levels is through a water change. Nitrites will eventually be converted to nitrate by the bacteria growing in the tank and filters. You want this reading to be 0 on your nitrite test.

pH is the scale used to measure the acidity or alkalinity of water. The scale ranges from 0 to 14 with 0 being the most acidic, 7 being neutral and 14 being the most alkaline. A pH test will tell you what your pH level is in your aquarium and out of your tap. It is possible to raise or lower your pH levels with water changes or chemicals (use extreme caution!) from your local pet store. Different fish species require different pH levels. Try to keep fish that all require relatively similar levels of pH. Here is an article with an interesting take on pH: pH : To be or not to be considered?

Phosphate can be introduced to your aquarium mainly from tap water, dead plants and fish food. High phosphate levels can cause algae outbreaks and can slow coral growth rates. There are products on the market to remove phosphates (check out biopellets) and you can do your part by keeping up with your aquarium maintenance and performing regular water changes with a Reverese Osmosis Water Filter. Saltwater reef tank keepers and freshwater plant keepers may want to invest in a Phosphate Test. The Hanna Digital Phosphate Checker is quite popular and easy to use.

Salinity Testing
This is the amount of dissolved salts in water and is measured using a Hydrometer or Refractometer. The hydrometer is usually the least expensive of the two but it's also considered the less accurate. Shell out the extra $25 for the refractometer. I've had issues with one of my reef tanks in the past where the plastic hydrometer that I was using was 2 clicks off - it was saying my water was 1.025 but it was actually 1.023 after testing it with a calibrated refractometer!

Specific Gravity
This is a density measurement for the amount of dissolved salts in saltwater compared to freshwater. Explained another way, saltwater is composed of many more elements than freshwater. The specific gravity measurement shows us how much heavier or denser saltwater is compared to freshwater.

Water Hardness
The hardness level of water has to do with the amount of minerals that are dissolved in the water. Calcium and magnesium are the primary minerals that are dissolved in tap water. "Soft" water has relatively few dissolved minerals whereas "hard" water has many dissolved minerals. Water hardness is not really an issue unless your water is excessively soft. Then you may have problems with runaway pH levels. For saltwater aquariums this is especially true. The carbonate hardness of saltwater can give you a good indication of how stable your pH is. Pick up a KH/GH test.

Below is a short video covering the basics of aquarium water testing and how to test your aquarium.

Aquarium Test Kit Comments

From: Renee - do I need a test kit?
I have 2 tanks both freshwater and both under 10 gallons. My Son (10) has a 7 gallon and my 6 year old son has a 2.5 gallon. We set up both tanks and we added starter fish, do we need to test these tanks? and for what exactly?
If you don't know about the aquarium nitrogen cycle, read that article and it will explain the parameters you will need to monitor on a new tank.

From: Amanda - recommended kit?
Is there a brand of test kit that you recommend? I have two 10 gallon tanks and plan to add a 20 gallon soon. Thanks!
I don't necessarily recommend one brand of aquarium test kit over another. I personally have used API, Seachem, Red Sea and Salifert test kits. I find myself using the Salifert test kits most often because I find them easier to administer and the color changes are clearly noticeable. If you shop online I'd recommend visiting several online retailers and reading the product comments to help make a decision. Also ask other hobbyists on the forum for their views. I do find myself using the Salifert tests most often. Mike

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