the dynamics of air in our tanks…

[Magnum Man54 169]

so we know that the surface of exposed air to the water directly relates to how much gas can be absorbed into the water, but in a different tangent, sponge filters seem to slowly clog, yet my long air bars seem to run freely for long periods of time without clogging… thissseemsvto indicate that the point where the air is coming out, is getting some sort of build up ( mine looks
like minerals ) possibly from evaporation of the water at the contact point??? the design of the contact point seems to effect this build up, and resulting restriction to air flow… I have several types of sponge filter connections some are just nipples the tube slides over, and some are a cross shaped fitting the tube slides over… these seem to. log faster, I assume because the interaction between the air and the water happens at the actual tube, and it is reduced by the cross shape the tube goes over… my air bars have many more opening for air to escape, all with various resistance, so as one begins to plug, and increases resistance that forces air to a new slightly more restrictive escape , so having kite places for the air to escape reduces the actual plugging of the device, I found this out back in the old undergravel filter days the smaller stones in the riser tubs plugged up pretty quickly requiring maintenance, and if I put a bigger air stone in the tube, it was a restriction for water, but the stones almost never plugged… Ivfound that while the tube was restricted by the bigger stone, the velocity around the stone increased and flow through the filter plate was still very acceptable…

so size seems to matter…

my biggest issue is with my small tanks ( 10 gallons ) the sponge filters are smaller, and seem to be constantly plugging up… seems like just when the tank is doing well, the foam filters air line begins plugging up, thus reducing the flow, and making the tank suffer, so as I get time, I’ll be looking at ways to make these smaller foam filters less maintenance…. the smaller tanks are less stable than the bigger ones, just because of their size and percentage of evaporation… it would be nice if the filters could be designed so that us one less thing to add to the instability..

and it’s interesting this plugging of the air lines… I used to just attribute it to minerals in my rock hard water… but I’ve been on RO for quite a while and still see the same plugging ( though less frequent ) so fish waste products must add to the plugging issues…

anyone have a maintenance free air powered aquarium filter

 

[davros2]

I seem to undersize my pumps, perhaps in the quest for quiet and thus alway suffer the clogging in short order. Those wands and strips seem to take lots of psi and volume

 

[davros2]

My stock of hob’s and internals are a bit much for my small tanks,regretting the 4 larger tanks I tossed when I last moved…

 

[Uberhoust4 3]

I don't have a lot of experience with air powered filters other than with the old styrene plastic corners filters from the 60's may be earlier, but I have used them for some setups. That said, I too have noticed that the small airstones seem to block quickly and I have wondered why. From my perspective there are two sources for the blockage, the air coming in from the pump, and the water flowing around stone. In regards to the air, there are impurities that get pulled into the air supply, I suspect some of this material blocks some of the air paths in the stone, forcing it to take a new route, with each blockage the overall flow slightly drops, the small stones have fewer pathways and will plug sooner. In regards to the water, introducing air to the water changes the chemistry of the water, if it has a lower CO2 content than the surrounding water the introduction of the air could make the water de-gas some CO2 leading to a less acidic water right near the airstone which potentially can lead to at least carbonate minerals coming out of solution, a similar effect can occur when there is cooling occurring which also occurs at the airstone (slight air pressure drop at the stone). I have seen mineral deposition both on airstones but also where the air leaves the water.

I live in an area now where my water is very soft and I no longer have any mineral deposits on my gear or in the tanks but my previous homes had water hardness in the 200 to 400 ppm range and there I did see a lot of minerals on my airstones (I use them for water flow not filtering), I tried removing them then soaking them in vinegar but that only partially worked. In the end I found some stones that are two pieces of plastic with one screwing into another, with small paths for the air to flow between them. These I found did not produce as small a bubble but could be taken out of the tank, taken apart and cleaned.

In regards to the sponges they will always clog up eventually. The sponge acts like a mechanical filter removing material as the water flows through its pores, but it also acts like a biofilter as that foam substrate is an ideal substrate for the biofilms. Biofilms themselves then attract and hold materials within the filter. As the filter ages from new to old it will cycle between high flow initially to lower flow but better filtering (due to biofilm establishment), finally ending up as a heavily colonized substrate that really has limited flow and is now quite a bit less effective as a filter. Ideally the foam filter should have a fine surface that will do the mechanical filtration but then have a zone of larger foam openings that will allow for significant biofilm development while still allowing significant water flow. In some regards I believe that many of the foam filters I have seen and worked with in the past have too fine of material for effective filtering. I have also found that foam with larger pores will often develop a biofilm and it is the biofilm that capture the fine particulate material from the water, though they too will clog eventually.

All filters will require maintenance eventually, some just require it sooner. For my personal experience I find that separating the mechanic filter components from the biomedia components lead to a filtration system that is easier to maintain even though it has more components. In the case of the foam filters you might extend the time between maintenance by simply putting a fine filter bag around the foam filter. This will keep the larger material from ever entering the foam keeping it in the tank where the fish and snails can get at it, before it goes into the filter where it is stored till you clean the filter. The mineral deposits and the air stone plugging I don't know what you can do other than accept it as something you have to monitor and deal with.

 

[TwoTankAmin46]

There is a big difference between an airstone and a foam filter. The airstone circulates air only. It clogs from debris landing in it are from the air when they have no intake filtration.. The foam filter uses air power to circulate water which contains what we want to filter out. Air does not pass through the foam only water does so. Of course if one puts an airstone next to a foam filter then the foam may pull some of the air bubble through the foam.

So, the foam sucks in all the mechanical waste in the water as well as any dissolved gasses. Of course, if ones' air pump is sucking is dust etc. in the air, those will go through the airstone. Many air pumps have a filter on their intake. This is usually replaceable. For the more common airpumps this is usually a form of floss like material.

 

[Uberhoust4 3]

So, the foam sucks in all the mechanical waste in the water as well as any dissolved gasses

I am curious by which processes the dissolved gases are removed by the foam.

 

[Back in the fold10 7]

You want to see something air driven really clog up ? The airline in a brine shrimp hatcher will sometimes clog in less than a day . I have a theory about this . The bubble momentarily leaves clear air that lets the water evaporate . This happens constantly thousands of times per hour and that’s how airlines clog up . Does that sound goofy ?

 

[TwoTankAmin46]

I am curious by which processes the dissolved gases are removed by the foam.

Well inside the foam there 0are colonies of microorganisms living. The nitrifying ones convert ammonia to nitrate in both one and two step processes. Those organisms use oxygen to do this. They also need inorganic carbon and they will get this from both CO2 and the carbonates and bicarbonates that mostly make up KH in tanks.

The nitrifiers live in a bio-film they create so they can stay attached to hard surfaces. Other heterotrophic bacteria will also colonize the bio-film. The nitrifiers are photophobic and prefer to live in darker places.

Because these microorganisms live in a fixed place, everything they need must come to them in the water. Where there are the greatest numbers of them living will be where they get a pretty continuous supply of what they need. In most tanks this is in filter media and also in the uppermost level of substrate. The media can include air powered. foam filters. Also, in tanks with plants rooted in the substrate, some plant swill transport oxygen from their leaves and stems down to their roots in anaerobic areas and release it there. This will allow the nitrifiers to live and function where they cannot do so in an unplanted substrate.

 

[Uberhoust4 3]

I guess I can see some oxygen removed, and some of the CO2 but I would expect the amount removed to be so small as to be indistinguishable from other changes to the equilibrium of the dissolved gasses in the aquarium. That said I really don't know.