Fish, Tanks and Ponds

Fish, Tanks and Ponds
A comprehensive guide to fish

Setting up a native marine aquarium

Marine aquarium
Marine aquarium

At some point most dedicated rock pooler will be tempted to bring home some of the interesting creatures they have come across so that they can learn more about them and enjoy the sites of the ocean form the comforts of home.


There are many different types, sizes and styles of tanks to fit any ones preferences. To make life easier, you should chose the biggest tank that you can possibly fit in your place. Most people make the mistake of thinking, "I'll just get a small one, to see if I can keep the fish alive before I invest a lot of money in the hobby." Speaking from first hand experience on this issue, you'll end up regretting it. Most hobbyists find that within a year of keeping marine fish they want to upgrade and have to buy new equipment for their larger tanks once again. However, the most important reason for getting a large tank to start with is that the larger water volume will be more forgiving of errors and a more stable environment for the inhabitants. I would recommend a tank with a minimum length of 24 inches.


The stand you chose to put your tank on is also a very important piece of furniture that can have many more uses then just holding the tank. It's a good place to be able to store all the many different foods, and accessories you will accumulate as well as housing any sort of external filtration units you wish to have or can even house a smaller tank called either a sump or refugium that can help out with filtration. It's best to get a stand specifically designed for an aquarium because a tank can be very heavy and regular furniture like a coffee table may not be able to hold the weight.


Lighting in a tank where only fish and possibly a few inverts will be housed isn't all that crucial. A regular tank light fixture with two bulbs in it would enough. There are many different types of lighting available along with different spectrums of bulbs. For a basic fish/invert only tank twin fluorescent bulbs a good choice would be to have one actinic bulb and one daylight bulb between 6,400K to 10,000K. The actinic bulb is recommended to provide more of the blue and violet lights that are more commonly found deeper in the ocean, will help bring out the colouration of your fish, and will mix with the daylight bulb to give off a nice clean white light in the tank.

However with this basic lighting you wont be able to keep any s life such as anemones and macro algae.; For this you will need more powerful marine lighting such as 4-6 T-5 bulbs, or metal halides.

Protein Skimmer

A protein skimmer is a very important piece of equipment for a Marine tank, it's the primary method of mechanical filtration and will pull out a lot of dissolved organic material from the water. A lot of research should be done before you pick out your skimmer to make sure it's the right one for your setup, easy to use and has a good reputation. This is one piece of equipment you don't want to just buy the cheapest one you can find because you will end up having to buy another one later on the works better or is easier to adjust.


There are many different kinds of substrates available for usage in a rockpool tank, again each has it's own set of advantages and disadvantages. The type of substrate you choose should be compatible with the types of fish you wish to keep. Fish like painted gobies naturally bury themselves in the substrate to hide from predators so you would need a soft sandy bottom, while something like Scorpionfish will be fine with larger rocks or even a bare bottom tank.

If at all possible, try to get some substrate material out of a mature setup or from the beach to add to your tank. (Before collecting sand/substrate materials from the shore lines, make sure you check with local by-laws to see if it's allowed.) This will also help speed up your cycling process. If it's not possible to get some of mature substrate, don't worry your substrate will eventually mature and become live, it may just take a little longer.

For more options see the article Choosing a substrate.


If you live close to the sea it's possible to collect your own water and use this in the tank.  For more information see the Collecting Natural Seawater article.
However if you live further from the ocean, it would be much easier to use a marine salt mix instead. There are many different types of salt on the market and it may be difficult to chose which one you want to use for your tank. There are many ongoing debates on which are best to use and which aren't that great. The truth of this matter is that all artificial salts available have it's own unique sets of problems and good points. 
One major caution you should be aware of is if you decide to change brands in the future (or even when you pick up a new batch of salt for that matter), you should mix some of the new salt in a container outside the tank with some of the old salt you were using in the tank and see if there is any sort of negative reaction. A negative reaction would be the salt not completely mixing, the water gets cloudy for a few hours or doesn't clear, or white precipitation on the bottom of your mixing container. If any of these symptoms appear, you either have incompatible salt mixes or a bad batch of salt and it shouldn't be used.

Power Heads

Power heads (a common abbreviation is PH, not to be confused with pH which is a water parameter) are small submersible pumps that are used to increase water circulation in an aquarium. There are many different sizes of PH's available for use in a tank. It's better to get two or three smaller PH's for your tank rather then one really powerful one.  This will make it easier to have gentle water flow through the tank. 

To help prevent fish from being stuck to PH intakes some manufacturers have created a basket that fits on the bottom where you can add filter floss or carbon for additional mechanical filtration which keeps the PH from getting clogged, thereby increasing the lifespan of the power head. There are also some PH's that swivel from side to side creating a more random movement in the tank.

Miscellaneous Items

Here are some extra optional items that you may wish to pick up to make things easier for keeping a tank:

Medium or Large net
Siphon and Gravel cleaner
Glass/Algae Scrubber
Water conditioner
RO/DI unit or water source
Dedicated buckets
Dedicated measuring cup for salt
Turkey baster
Extra powerhead
Log book

Mixing the Water

Water quality and stability is probably the most important issue you will need to learn about when caring for a marine tank. Marine animals come from an environment that is extremely stable with very little fluctuation in temperature or salinity. In nature the water is pristine and constantly being placed by waves, tides and currents. In our tanks, we change out very little of the water very seldom. We attempt to mimic the motion found in the ocean through the use of water circulation devices and filtration units, but it doesn't come close to what wild animals are provided with. Therefore, it's extremely important to remain vigilant when adding water to the tank. No matter what kind of artificial salt mix you pick up for the tank it will not be exactly the same as natural salt water (NSW).
All commercially available salt mixes are formulated for use with distilled water. This was done to insure that no matter where salt was mixed up they would have the same chemical composition regardless of the variations of local water supplies.
Ideally we should also use distilled water to add the salt to, however in most cases this is impractical and expensive. In addition to the expense of distilled water, most distilleries use copper piping to cool the steam down. This leads to the potential of the distilled water being contaminated with copper, which is a very toxic substance in a marine tank.

A second option, which is highly recommended, is to use RO/DI water (Reverse Osmosis / De-ionization). The price of purchasing an RO/DI unit is come down dramatically within the last couple years making them more commonly available to have in your own home. RO/DI water is filtered water so it isn't 100% pure but with a unit in good working order, you can get it close enough that you needn't worry about harmful contaminants.

Tap water, although extremely handy, isn't all that reliable. It has the potential of having many harmful toxins in it and should be tested before being used in a marine tank, especially for phosphates, ammonia, nitrites, nitrates, copper and other heavy metals. It's also important to know that what you test today may not be what you will get out of the tap tomorrow. Should tap water be used it will need to be conditioned to remove chlorines and chloramines that is commonly added to make it safe for drinking, but is toxic to fish and invertebrates. Make sure you read the labels on any water conditioner carefully to ensure the proper dosage. Do not over dose or under dose the conditioner or you may run into other problems in your tank, mainly with your protein skimmer. The pH of tap water may also need to be adjusted if it's too low. This can be done using a marine buffer or Kalkweisser (lime water).

To make future water changes easier, it's best that you have one container dedicated to mixing your saltwater in. This way you can get used to how much salt to add to that particular container to be close to the specific gravity (SG) you have in the tank instead of guessing all the time. Different salt mixes will require different amounts of salt, but should be fairly similar measurements. A SG between 1.022 to 1.025 will be fine.

Setting up the Tank


1, Heavy traffic areas: this will unduly stress the fish out and they will tend to hide a lot more
2, In Front of Windows, AC outlets or Heaters: This will cause the tank to either over heat or have larger temperature fluctuations then the fish will like. Also, make sure that you don't place the tank in places it will get direct light from the window or have the sun reflect off the glass that will impair your viewing of the tank.
3, In front of doors or other moving objects: You don't want anything to swing and hit the tank and break the glass!

Good Locations:

1, Near power outlets. The importance of this can't be understated, you will have many power cords for your tank and you don't want to have to use long extension cords to power your tank.
2, Make sure you can place the tank a minimum of 6 inches away from the wall. There will be times when you need to get behind the tank to adjust power cords, clean the glass, look for a missing fish, hang equipment pick up that fallen net, etc.
3, The closer to your water source the better. You will need to maintain the tank, do water changes and top-off the water in the tank due to evaporation, the less work it is to haul water back and forth, the more likely you will keep doing those important maintenance tasks on your tank.
4, Ensure the area the tank will be sitting on is level. This will allow weight to be distributed evenly and reduce the potential for the tank cracking once the water, substrate and rocks are in place. Use a sheet of polystyrene insulating material for the tank to sit on to help.
5, Make sure the tank is easily accessible for reaching into and watching when you aren't working on it. The more accessible the tank is, the less hassle maintenance will be and the more enjoyable the tank will become.

Before filling your tank up and adding all the equipment it's a good idea to leave the tank on the stand in the location you have chose for it for a day or two to make sure that's where you really want it and to see if there is something about the location you don't like. Once the tank is set up it's a lot of work to take it down again to move it because of a poor choice of location.

Once you have the location chosen and are satisfied with where you want the tank, it's time to start setting things up. Make sure the stand is level. Once it's levelled off, place the polystyrene insulating on top of the stand and then the tank. The polystyrene will compensate for any flaws in the stand. That done you can add the substrate to the tank. If you got the substrate from an open bin in the LFS then it's best that you rinse it off thoroughly to help avoid contamination. If your substrate came from a bag, it's not necessary to rinse it off, the smaller particles on the substrate will be good for bacteria to grow on, but the water will be cloudy for a few days.

Now that you have the tank level with the substrate in, it's time to get the water ready. It's best that you premix the water before you add it to the tank so that you can be sure that all the salt dissolves ahead of time. If you mix the water in the tank, you run the risk of having some extra salt settle in the substrate and slowly dissolve during the days ahead and slowly raise your salinity. If you don't have the room to mix up the salt water outside the tank, then it's better to mix a hyper saline brine solution in a smaller container and slowly add the brine to the water in the tank until you get a specific gravity reading between 1.022 to 1.025. Only fill the tank about 1/2 to 3/4 full to allow for water displacement when you add the rock/decorations and remaining equipment to the tank.

Helpful hint:

 Before you add the equipment to the tank, you may wish to take this opportunity to label all your equipment just above the plug. Once you get everything into the tank and start plugging equipment in the cords will quickly become jumbled and can be difficult and annoying later on to figure out which plug is which.

Now you can add the remainder of your equipment to the tank and start placing your rocks or other decorations. Take your time and have fun aquascaping your tank! If at all possible, avoid resting rocks on the walls of the tank, this will limit the water circulation in the tank and will make it difficult to clean the algae from glass later on. However, in smaller tanks this may be very difficult, in this case, make sure that you have some way of getting decent water movement in behind the rocks so you don't get detritus build ups that will pollute the water. Make sure that the rock work is sturdy and rocks wont fall over should something bump the rock or tank. This could lead to a fish injury or worse the rock hitting the glass and breaking it. Try to provide as many hiding places as possible. The more comfortable a fish feels in the tank, the less stress it will experience and the less it will hide, use your imagination and have fun! Try a few different set ups to see what you like before you add fish to the tank, after you have fish in the tank it'll be more stressful on them should you constantly be rearranging their home.

Once you've finished adding all the equipment and decided on how you would like your rocks placed, top off the water in the tank, plug everything in and make sure all your equipment is working. Check the salinity in the tank and make sure it hasn't changed. It's also a good idea to take some baseline measurements for pH, Salinity, Temperature, Calcium, Alkalinity, ammonia, nitrite and nitrate and log them in a book so you can see any sort of patterns emerging as the tank matures.

Maturing the Tank

Once the tank is set up, it's time to wait for the tank to mature. This is the thing, which catches out most people when starting a new aquarium, for some reason it is hardly ever explained properly when a tank is purchased, and quite often the wrong advice altogether is given. The filters need to grow a colony of helpful bacteria to breakdown the toxic water in the aquarium water. This won't happen simply by leaving the tank without fish for a few days after it has been set up. The process actually takes from 4 to 8 weeks and until it is complete NO fish should be added because there is a very high risk of them dying.

Methods of Maturing the Tank

Method one, Set the tank up and leave it all running for a few days Inc lights filters everything. After a few days the tank will go cloudy due to a population explosion of mobile bacteria as they feed on dissolved organic material in the water and anything else trapped in the gravel etc. This will soon clear as there is a very limited supply of food for them and once it is used the tank will clear of its own accord.

At this stage a couple of hardy fish can be put into the tank and when this happens the Ammonia level will begin to rise. Because fish excrete Ammonia through there gills and any waste they pass will also be changed into Ammonia as described at the beginning of this message. The mobile bacteria, which produce the Ammonia, can multiply very rapidly and so Ammonia levels will rise rapidly too.

Unfortunately the bacteria which oxidize Ammonia and make it into Nitrite don't multiply quite so fast and it could take up to a week at tropical temperatures for them to start oxidizing the Ammonia effectively during which time the ammonia levels will continue to rise.

After about a week or so the Ammonia levels will start to fall as the bacteria get to work on it and as a result the Nitrite levels will begin to rise. Again the bacteria which convert Nitrite to Nitrate are slow to grow and they don't like conditions where a lot of Ammonia is present so they won't really begin to thrive until there is some Nitrite present and the Ammonia has almost gone. This could take 2 to 4 weeks during which time the Nitrite levels will rise.

Finally another type of specialized bacteria will begin to grow and convert the nitrite into nitrate and gradually the Nitrite levels will drop until they eventually reach a level where they can't be detected. At this point the tank is cycled.

Advantages of this method - none
Disadvantages - It subjects the fish to high levels of toxins, which will harm them and could kill them.

Method Two Fishless Cycling with Live Rock, This is the most popular method of cycling a marine tank. This can be done using either cured live rock or uncured live rock. Using cured live rock will give you a nearly instantly cycled tank. It's best to wait about a week and test for a small cycle to occur. When using cured live rock it's possible that you wont get any ammonia or nitrite readings, but you should see a slight rise in nitrates, at this point it's safe to add fish slowly! Unfortunately, cured live rock generally comes at a premium price however there is a less expensive method available as well, uncured live rock. Using uncured live rock will take more time, but the end results will be the same.

Advantages - Can be nearly instant with Cured live rock, kinder to fish. Live rock also introduces many small life forms into the tank increasing the biodiversity, provides a small natural food source for fish and is vital for complete de-nitrification within the tank.
Disadvantages - can be time consuming when using uncured live rock.

The First Fish

Once the ammonia and nitrite levels both read 0ppm, it's safe to add your first fish or two. Remember to go slowly or else you risk going through another cycle and harming your fish. Even though there is enough bacteria in the system to handle some ammonia and nitrite, the system isn't completely stable yet and wont be able to handle a sudden large bio-load.

Signs of a good fish.

All its fins should be erect and it eyes clear from any cloudiness
It should be free of any deformities.
It should be alert and interacting with its surroundings.
It should look to be reasonably well fed and not hollow bellied.
It should be free from sores and blemishes.

Poor Fish.

Always reject any fish with any of the following.
Fish that look hollow bellied or pinched behind their heads. These fish will not last long.
Any fish with open sores or frayed fins. The chances are they are carrying a bacterial infection and could be contagious.

Transporting the fish

If you don't live too far from the rockpools you will be collecting the fish from, an open bucket should suffice.  However if you are travelling further afield it would be best to place them in plastic bags. It isn't unknown for fish to become trapped in the corners of these bags and die on the way home. Yet this is so easily avoided. You can use rubber bands to tie up the corners of the bag or double bag where one bag is placed upside down in another this has the advantage of offering some protection against a leak too.

Introducing the fish into the tank

Rockpool fish are very hardy animals and should be fairly easy to introduce to an established tank.  You don't need to worry about sudden temperature changes or salinity changes because they are used to these drastic changes in the wild.
If you want to make it a little easier on the fish you can float a pail or bag in the water for a while until the temperatures match.

If you used a bag to transport the fish, cut open the plastic bag; don't puncture it using your fingers because this could damage the fish's swim bladder through the sudden increase and decrease in pressure.

If you are using natural seawater for the tank then you can slowly tip the pale or bag into the tank and allow the fish to swim out on it's own.
If you don't want to add the water from ocean into the tank because of the potential for introducing diseases or pathogens from the ocean, carefully net the fish and then put the fish into the tank as quickly as possible. Allow the fish to swim out of the net on it's own.
If there are already some fish present in the tank feed them about an hour before the new fish are added and give them another small feed immediately after the new fish have been introduced. This will allow the new fish time to settle without being threatened by the established residents.


Rockpool fish are generally opportunistic feeders and will readily accept any foods offered to them in a tank. They will accept fresh, frozen, flake, and freeze dried foods. A good variety of meaty and vegetative foods should be fed to them. Ideally they should be fed small amounts of food a couple times a day.

Tank Maintenance:

Once the tank has been completely cycled, a good water change is required along with a quick rinse of the filter media and cleaning the glass.


Turn lights on
Check tank temperature
Check to see all fish are accounted for
Check skimmer to see if its working
Top off water with fresh RO/DI water, not saltwater
Feed fish
Clean glass


10 to 20% water change
Check Ammonia, nitrite, Nitrate, pH, SG, Calcium, Alkalinity, Phosphate, and Copper levels
Clean out skimmer cup
Blast live rocks to remove as much debris as possible
Vacuum substrate


Clean out skimmer
Clean powerheads


Change lights


Rockpool fish are susceptible to a number of different diseases such as Cryptocaryon (ich), Amyloodinium (marine velvet), Brooklynella (clownfish disease) and Head and lateral line erosion (HLLE). Make sure that you have some appropriate remedies on hand and if at all possible quarantine any new catches before adding them to the main tank.