Air pumps are those buzzing boxes that can be felt to vibrate slightly when touched. Another type of air pump uses a piston attached to a revolving wheel, which gets rid of the buzz and the vibration but only pushes air at the compression stroke of the piston. The latter type has never been used much by the hobbyist.
The air pump was, and possibly still is, used extensively by fresh water aquarists. In the earlier days of the marine hobby it found favour as well.
Nowadays it is unusual to find an air pump in use on the marine display aquarium as the role has been taken up by powerheads and the like. This is a good thing as there were problems with the air pump.
Reliability wasn’t a particular problem though of course routine maintenance had to be done, comprised of checking the air ‘stone’ and occasionally the diaghram inside the pump housing. The problems were secondary rather than primary.
The reason for using the pumps was first to try to ensure that the seawater was oxygenated. Then it was to create seawater currents. Finally it was to operate the early protein skimmers, once they had arrived on the scene.
The aquarist would position the air ‘stone’ (called a stone but normally made of wood as the bubbles created were small) so that a small ‘mound’ of seawater was created at the surface. This was important as the splash from the bubbles would be minimized. This annoying splash could never be completely eliminated and there would always be salt deposits above the mound if there was anything there, such as wires or cover glasses, for the splashes to land on. Oxygen would get into the seawater not from the bubbles, though a little would enter from them, but mainly because the flow of bubbles lifted a column of seawater to the surface, an air/water interface. When the seawater curled over at the surface and moved downwards and sideways, it would do so all round the mound creating random movement. An air stone was used on the air driven protein skimmers as the tiny bubbles created were helpful in increasing the efficiency of the device, though the air stone needed regularly renewing.
Protein skimmers are now for the most part motor driven and far more efficient. Air driven skimmers are still for sale and may be used here and there but are much less popular. So that’s one area where the need for an air pump has generally gone.
Air pumps are not used for oxygenation or circulation anymore as they cannot compete with, for example, the powerhead. The powerhead circulates the seawater very well and, provided the aquarist has positioned the units carefully, the currents produced are chaotic and random. Seawater oxygen is well catered for as the efficient circulation should bring seawater to air/water interfaces continuously.
The need for an air pump in the marine hobby has nearly gone. Why nearly? Well, they are still useful when a routine seawater change mix is being prepared. An air pump will be easily efficient enough to turn the seawater over permitting oxygenation and heating. It is true a powerhead could be used, but a small air pump is good enough if the aquarist wants to follow this route.
There is one more role, and this is where the aquarist finds that there is a continuous slightly low pH reading and it is puzzling why. This could be to do with oxygenation and the efficient movement of seawater to air/water interfaces. To check is simple. Remove say two gallons or so (the amount is not critical) of seawater from the aquarium and place it in a seawater safe container (the routine seawater change mixing bucket is ideal). Put the heater normally used into the bucket and also the air stone, just as in a routine seawater preparation. Allow it to aerate for around two hours, again the exact timing is not critical. Then measure the aquarium pH before returning the tested seawater to the aquarium, and rinse the hydrometer in fresh water. Drain the hydrometer as well as possible then, using seawater from the bucket, rinse the hydrometer to ensure any fresh water is cleared. Then test the pH level. If the pH level is higher than in the display aquarium it suggests there is a gas exchange problem.
The seawater in the bucket can be returned to the aquarium.
The aquarist must now consider how gas exchange could be improved. The first thing is to check if the powerheads or other devices in use are circulating the seawater sufficiently as given in the guidelines for different type displays – if not increase the circulation. If the circulation appears to be fine, then are the currents generated as they should be, that is random and chaotic? If not, adjust the circulation devices so that they are.
It could be that all the checks in the previous paragraph are fine. If so then try running an air pump in the display aquarium. This will be for a test period of, say, a week. As mentioned earlier adjustment will be needed to minimize splashing. This could well be the answer to the pH problem. The display aquarium is the first choice but if necessary the air pump stone can go in the sump, though this will possibly not be so effective. Check the pH two or three times during the week, if it has risen great.
There isn’t a need to go and buy another air pump as the one in the aquarium can be removed after the test. It can now go back to routine seawater change mixing.
There is a need to purchase a new powerhead, which will replace the air pump in the aquarium. This new powerhead should be placed in the display aquarium if that is practical, or as a second choice in the sump. This time the powerhead will not have the output set horizontally but vertically. The powerhead could be placed at one end or the other or at the back to minimize visual impact. Seawater will be continuously and efficiently lifted to the surface, where a fairly large mound of seawater should form – there shouldn’t be any salt splash as there aren’t any bubbles. The flow of the seawater coming off this mound will not be detrimental to the flow already present.
It is best if the new powerhead is placed fairly low down in the aquarium so that lower seawater is lifted, but it should remain accessible for maintenance. Different aquariums have different depths and obviously the powerhead should be capable of lifting the seawater from the required depth. To obtain a guideline, temporarily detach a powerhead and put it at the required depth pointing upwards. Is there a good mound of seawater created? If so, the needed power of the new powerhead will be known, it is the same as the one already in use. If not, obtain a more powerful one.
So, as can be seen, the air pump is not necessarily obsolete just yet.