Water: the essential element for fish

The texture of good quality water is subtle

Water: the essential element for fish

The texture of good quality water is subtle
The texture of good quality water is subtle

On a very basic level water is 99.98% H2O in a liquid that your fish swim, eat, breathe and excrete into. What about the other .02%? Is it important? Of course it is. It is these minute quantities of dissolved gases and dissolved solids that makes all the difference in whether the water is hospitable or poisonous to the fish. It is this 0.02% of dissolved substances that make sea water, river water and lake water different from each other. Note that seawater has a much higher level of dissolved salts of around 3.5%. It only takes minute quantities of the common gases such as ammonia, carbon dioxide or insufficient oxygen to poison or drown fish. Likewise it only takes a small amount of pollution or the wrong type of chemical to be dissolved in the water to poison and kill fish. But when conditions are just right or within reason then your fish will thrive without much care from you.

Creating a generic biotope for your fish to live in

The most common elements of an aquarium biotope
The most common elements of a biotope

As a fish keeper is is your responsibility to recreate a reasonable biotope for your fish that is as close as possible to the fish’s natural environment as you can.

Water has dissolved gases such as oxygen, carbon dioxide, nitrogen, ammonia and chlorine. Some of these gases are poisonous while others are necessary for fish to breathe. Water also contains dissolved minerals that determine the general hardness of your water. Some fish thrive in very hard water with a high ph, while other fish prefer much softer water with a lower ph. Organic matter can also dissolve in the water, usually darkening the water and acidifying it.

A biotope should include a substrate, plants and a source of light with the temperature of the water kept within a suitable range for the plants and fish. The choice of subrate includes gravel, sand, and even soil. Soil is usually topped with gravel. Other less essential features you might want to include in your fish’s biotope could include rocks, roots and branches.

The Lake Malawi Biotope explained here

The Amazon Biotope explained here

Is tap water safe for fish?

Is tap water safe for fish
Is tap water safe for fish

Tap water direct from the tap is not suitable for use in an aquarium. The main problem is chorine which water companies put in the water to kill off any potential bacteria in the water. To remedy this you need to leave your tap water standing in a container for at least 24 hours. This allows the chlorine to evaporate. This can be achieved by using buckets of water or water barrels to store the water.

Another danger to your fish is from dissolved copper which can come from copper pipes. Water that comes into contact with copper will slowly absorb the copper. This problem is worse for new copper pipes. But this can be remedied by running your tap water for a few minutes until uncontaminated water starts to come through. Copper is poisonous and even copper coins left in your aquarium will slowly dissolve and kill your fish.

If you are going to be serious about the quality of your fish’s water then you should buy a water test kit. A good test kit will test ph, ammonia, nitrite and nitrate as well as general hardness.

If you are a new fish keeper who wants the best chance of keeping your fish healthy and alive then test your tap water before you buy any fish. When you know the ph and hardness of your water then you can buy fish that prefer the water from your tap. Adjusting your water to suit fish that like a different type of water is best left to the advanced aquarist who don’t mind the extra effort. Some fish when kept in the wrong type of water will simply die after a few weeks and certainly won’t thrive.

If you are a more experienced aquarist then you can start adjusting the ph and hardness of your tap water so that you can keep the more delicate species of fish. To soften your water you can buy a reverse osmosis device that will remove the minerals from your water. Such water is usually too soft and must be mixed with unfiltered tap water to achieve the correct level of hardness. You can also use rainwater collected from a safe source.

To adjust the ph of your water you can either use a muslin bag containing peat moss to acidify your water or you can use calcium carbonate sand to alkalinify it instead. In order to reach the correct ph level.

All these procedures are complicated and time consuming and even prone to error. Messing with your tap water usually means you will have to monitor changes in your water conditions to maintain it. To make this complicated process a little easier it is best to prepare large batches of water in say a 200 litre barrel all in one go and then draw off water as needed.

I recommend that you don’t bother with all this messing around and just buy fish that can do well in the water that comes from your tap. There is usually quite a variety of fish that will suit your water conditions but you may have to avoid a particular species of fish that you might be keen on.

What water conditions are best for fish?

Normally the ph used in most freshwater aquaria ranges between 6.0ph and 8.3 ph. However Lake Tanganyika fish like an even higher ph, even as high as 9.0ph. And they also like hard water. Ph nearly always varies together with hardness. High ph above 8.0 usually means very hard water, while low ph of 6.4 or less coincides with soft water. Some amazonian fish like water that is of a ph less than 6ph and have very soft water.

Most of the commonly available fish in your aquarium prefer an average ph around 7ph and a medium level of water hardness. Not only that but such species can also tolerate a wider variation away from this medium than other more exotic species. Tank bred fish that have been bred in aquaria for several generations are overall more adaptable to variations in aquarium conditions compared to their wild caught counterparts.

Most average species will live in a wide range of possible water condititions. However, when it comes to breeding the ph and hardness must more closely resemble the fish’s conditions in the wild. Only then will some fish be capable of breeding and their eggs hatching.
Water hardness

This is a measure of the amount of dissolved minerals in your fish’s water. The most common minerals are calcium, magnesium and sodium.

These dissolved minerals are also essential for the health of your fish and plants.
Most cyprinids, tetras, rasboras and similar river fish like soft water. Most livebearers, Malawi fish and Tangayikan fish prefer quite hard water.

Plants also show a similar type of preference for different levels of hardness depending on the plant species.

Iron for fish health

Plants require minute levels of dissolved iron for optimum health as do fish. Fish acquite iron from their diet while plants will absorb it directly from the water. Pure iron quickly rusts in water making it unusable for the plants and animals. Feeding fish iron rich fish food will not only provide iron for the fish but allow the fish to provide manure that is rich in iron for the plants use.

Dissolved oxygen in water that fish breathe

Dissolved oxygen is essential for fish to breathe. The main source of oxygen in an aquarium is through the surface of the water. So a large surface area of water is essential to allow sufficient oxygen to dissolve into the water to replace the amount of oxygen that the fish breathe in through their gills. Also excess carbon dioxide that the fish release into the water from their gills has to be released from the water through the surface of the water. Plants also give off oxygen when they are in bright light, but will release a small quantity of carbon dioxide at night.

It is best not to rely on the quantity of oxygen that plants produce during the day to supplement the amount from the surface because this source of oxygen stops at night. If you see your fish gasping for air very early morning this is a sign that there is not enough oxygen and too much carbon dioxide in the water in the night so you will have to reduce the number of fish in the aquarium. This can also be a sign you have too many plants.

Fish waste in water

One lethal cause of fish deaths is ammonia poisoning which burns the skin and gills of the fish while also displacing oxygen in the water. Ammonia comes from fish waste and from decaying fish food and other decaying organic matter. In a new aquarium there will be no ammonia but this will build up over the fish few weeks. If you are new to fish keeping you will see your fish as being fine for the first week and may not realised that the fish are slowly but surely poisoning themselves in their own waste matter.

To overcome this you need some way to remove the ammonia as it gets created. You will have to for the first 6 weeks have to do daily water changes, use a filter and make sure that you under stock your tank until it is mature. Also avoid any uneaten fish food being left in the tank that will quickly rot and cause an ammonia spike.

A filter is not just for removing particles from the water but also for providing a base for the growth of bacteria that digest ammonia converting it into nitrite which is also poisonous. Later on another set of bacteria develops that will digest the nitrite converting it into nitrate which is much less harmful. This process takes between 4-6 weeks from new. So partial water changes are needed daily until the filter matures.

This is better explained in cycling your aquarium

Plants take up nitrate but usually not enough so you will need to keep doing partial water changes, perhaps once a week. 10% of the water changed is a reasonable amount of water change.

During this filter maturation period you should test your water daily with a test kit and if the ammonia or nitrite reading becomes particularly high then you will have to do another partial water change to bring it down to acceptable levels.

The nano marine aquarium

The fascination of the nano marine aquarium

Larger aquariums are better than nano marine aquariums if you have the money

If you are a newbie marine aquarist, then you may be tempted by the lower cost of buying a smaller aquarium. Or you don’t want to commit to a larger aquarium until you know you can look after aquarium fish. So you might buy a smaller tank as a trial. This can be a mistake. If your dealer is persuading you to buy a larger tank then listen to him, if you can.

A small aquarium, especially a marine aquarium, is more difficult to cope with because of sudden water quality problems. In a bigger aquarium these problems are diluted by the larger quantity of water. Any rise or fall in salinity, pollution or other water parameter will be much slower in a large aquarium than a small aquarium. It is a falsity to believe a small aquarium is easier to maintain than a bigger aquarium. The opposite is true.

A freshwater nano aquarium is certainly much easier

List of beginners recommended saltwater fish

Comparison of large aquariums with nano marine aquariums

You will still need to buy all the same equipment for a nano aquarium as a large reef aquarium. For example hygrometer and water test kits. Some of the equipment is just miniaturised versions of the ones available for large aquariums, but the price is not miniaturised being about the same price. Savings in costs are usually made in the price of the aquarium, stand or cabinet, price of lighting, costs of live rock, cost of live stock because you will only be able to keep a small number of fish and invertebrates. Smaller heaters are a little cheaper. But the rest of the equipment is about the same, including on going costs.

Your first foray into keeping a marine aquarium will have a greater chance of success if your choice of tank size is at least 160 litres. With a tank of less than 160 litres, monitoring and maintenance work doubles. You will have to buy a good quality test kit that is easy to use and you will have to keep using it daily or even twice a day. The water has to be checked daily for salinity levels, ammonia, nitrites and nitrates. Adjustments and interventions will almost certainly have to be made more often. Things change so fast in such a small aquarium that salinity levels due to evaporation or pollution levels may change quickly and kill your fish or invertebrates in a day. In a larger aquarium these changes are slower and your fish have more time to adapt. And there is more opportunity for you to catch these dangers and correct them in time.

Beginners saltwater aquarium here

First Saltwater aquarium here

Stocking the nano marine aquarium

For many aquarists the prohibited costs of the larger aquariums leave them with no option but to start with a smaller aquarium. To be successful in a smaller aquarium your choice of fish and invertebrates must be made with more care. Corals from shallower waters are more tolerant of changes to water conditions than their deeper water counterparts. Also, your choice of fish is limited to the smaller and hardier species. Common clownfish, pyjama cardinalfish, dwarf angelfish and neon gobies make the best choices for the smaller aquarium and are great beginner fish anyway.

Once you have fish in a smaller marine aquarium then your options for invertebrates becomes limited both in the number and range of invertebrates you can successfully keep together with your fish. Shrimps and small hermit crabs are the hardiest invertebrates that might survive with fish present.

It is better to understock and overfilter for the first few months. It will take this long for your filters, live rock and live sand to fully mature. In this period you will get practice and experience of running your aquarium.

Maintenance of your nano marine aquarium

More careful attention to the diet and especially the feeding has to be made to make sure that the fish are well fed without allowing waste food to occur that will pollute the aquarium. If you good have experience in keeping fish then you will know what to do. For the less experienced, great attention has to be made to uneaten bits of food.

In a smaller aquarium it is better to have a protein skimmer and a uv filter. But don’t overdo it. The protein skimmer will remove essential nutrients while the UV filter may kill off helpful plankton. You must have live rock and live sand which will provide biological filtration. Once established this will greatly enhance your chance of succeeding.

You will have to buy the live rock. Cured live rock is better but more expensive than uncured live rock. Uncured live rock will cure in your aquarium. The effect of this is that pollutants from dying organisms will seep into your aquarium water for weeks until the rock cures. The live sand will develop by the migration of microscopic lifeforms and bacteria from the live rock into your sand. Also have a good external filter to perform additional biological filtration. Remove excess waste from the filter media by squeezing out once a week. Do not rinse out or you will lose the nitrifying bacteria.

Buying several small pieces of live rock and plenty of ocean rock is one way to create enough live rock in your aquarium but you will have to wait while the life from the live rock migrates to the ocean rock. This process takes time. if you have the patience then you can save money this way. Remember live rock will start to die when not submerged in sea water. Newly bought live rock from your dealer needs to be kept in seawater on the way back home. Make sure you buy solid live rock and ocean that is not prone to crumbling.

It is highly recommended to do many small partial water changes to the nano aquarium. Have a large container of pre-mixed saltwater. This will reduce the amount of times you have to mix water and sea salt to create seawater. The use of reverse osmosis water is highly recommended. Buy a RO water kit that will convert your tap water into pure water. Otherwise you will be spending a small fortune on continually buying RO water from your dealer.

Self contained nano marine aquariums

There are many self contained nano aquariums. These have advantages and disadvantages. Some are enclosed systems that reduce the water evaporation. The downside to this is that they tend to overheat, because of the enclosed lighting, especially in summer. The open top varieties are better in this regard but will require topping up with water daily to maintain the required salinity. Because of their all in one nature, these aquarium set ups work out cheaper. But invariably modifications will be necessary to these set ups to make them work.


Today, you have a better chance than ever before of having a successful nano aquarium because of
1. Advances in technology of filtration, monitoring and maintenance equipment
2. The wider availability of aquarium bred fish
3. Wide availability of good knowledge of the marine aquarium environment
4. The price of marine fish and live rock is falling because of the success of home produced sources
So, why not give it a try and start enjoying the colourful world of marine fish.











You can buy clownfish and dwarf angelfish online with home delivery in the US.

Featuring Angelfish