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Air stone?

S

Simon25

Member
Joined
5 Oct 2021
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35
Location
Southend
Hi All,
I have a planted tank (about 7 plants so far) but the fish seem lethargic. My filter gives loads of surface agitation. Do I need an air stone? As when I put my filter to pump bubbles as well the fish seem more lively… I would of thought the plants would of given enough oxygen in the water with the surface agitation as well.
 
Worth doing a water change, and assessing again tomorrow. I run air stones, it doesn't hurt.
 
castle said:
Worth doing a water change, and assessing again tomorrow. I run air stones, it doesn't hurt.
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I did do a big water change 2 days ago hasn’t made much difference to the fish 😩. Yea I might run an air stone but for aesthetics I don’t like the bubbles running in the water lol
 
You haven't given a great deal of information, there is a page on here which lists useful info for diagnosing problems, I'm sure someone will be able to supply a link!
Things such as tank volume, age of set up, type of substrate, when & how many fish added, type of planting etc.
You could be having a mini ammonia or nitrite spike for some reason, you're obviously concerned all is not well so continuing with a small daily water change would be a good idea until everything settles down or you find the cause.
 
So on the topic of bubbles. Small bubbles are better because they have a larger surface area to volume ratio. If you had 40 bubbles that were 2.5 mm in diameter, then you would have added 78.5 cm squared of surface area for air exchange. For 40 bubbles that are 1 mm in diameter, then you would have added 12.5 cm squared of surface area for air exchange. But in reality you would produce far more small bubbles given the volume of air that you pumped in. A 60 cm by 30 cm aquarium has 1800 cm squared of air exchange surface area, so you would need 5760 bubbles at 1mm diameter to match air exchange achieved by the surface of an aquarium of that size. This indicates that air stones are fairly worthless if you already have surface agitation.

A better place to look might be things like: temperature (hot water hold less dissolved oxygen), diet (metabolism), disease, light intensity and shade-cover, carbon dioxide levels, and other toxins (like nitrite) that are attributed to lethargic fish behaviour. There are a few factors that can reduce dissolved oxygen levels also, so your best place to start would be to give members full details, see here. Then they will be more informed. I would also detail exactly what behaviour you are witnessing in which species, their age, diet, feeding regime, and other factors like nearby noise and vibration that can make fish more timid.
 
The Miniaturist said:
You haven't given a great deal of information, there is a page on here which lists useful info for diagnosing problems, I'm sure someone will be able to supply a link!
Things such as tank volume, age of set up, type of substrate, when & how many fish added, type of planting etc.
You could be having a mini ammonia or nitrite spike for some reason, you're obviously concerned all is not well so continuing with a small daily water change would be a good idea until everything settles down or you find the cause.
Click to expand...
The tank has been running for easy 6 months, there is only 6 fish, 9 shrimp and 6 snails. The plants I have I don’t really know their names I know 2 of them are Java ferns. The size of the tank is 180ltr. Substrate is just normal fluval substrate nothing else.
 
Simon25 said:
The tank has been running for easy 6 months, there is only 6 fish, 9 shrimp and 6 snails. The plants I have I don’t really know their names I know 2 of them are Java ferns. The size of the tank is 180ltr. Substrate is just normal fluval substrate nothing else.
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Can you post a picture? You also need to post test results of your water parameters.
 
Simon Cole said:
This indicates that air stones are fairly worthless if you already have surface agitation.
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Are they? I think the velocity of bubbles exceeds that of the surface and the boundary diffusion layer is thinner. That promotes the rate of diffusion. Second, air stones help to move water vertically, which is of importance, too. I wouldn't go as far as deeming air stones 'fairly worthless'. ;)
 
@_Maq_
I agree. Bubble velocity is going to be below 0.67 miles per hour (30 cm per second). I would imagine that the surface agitation (velocity) with an modest filter would average at about 10 cm per second (about 1/3 the velocity) at the water surface (excluding considerations of air velocity on the other side of the boundary). The calculations look a bit uninviting, so taking this on face value, I would presume that 1,920 bubbles would be required at 1mm diameter in order to match the air exchange achieved by a modest filter at the surface water interface for an aquarium of that size. But for a powerful filter with good water surface agitation, then these benefits will be dramatically reduced. I do think that achieving anywhere near 1,900 bubbles is going to require a decent air stone and a suitable pump. Something like this:
1658044228960.png
1658044319297.png

Most of my filters are a lot more powerful, and I usually have a lily pipe or something near the surface to vortex air down and out, and often I will have a skimmer somewhere too, or even two filters. So I'm easily surpassing any of these problems, but I do see a place for air stones in the hobby. In terms of the value, it is a bit harder to judge. There must come a point where oxygen becomes saturated. Air stones have a lot more saliency if the purpose is to lower carbon dioxide levels.
Both @Geoffrey Rea and @JoshP12 have run a few experiments with dissolved oxygen (DO) probes. There is a rather juicy discussion on <page 4 of this thread>. I am a rather lazy guy - I had an (MCERTS) DO probe for several years but never used it, and to be honest, I would probably just drop the temperature of my water down or adjust my carbon dioxide, in-lieu of setting up an air stone. But I have used them quite a bit in several of my tanks, especially when I am working with a medicine that is known to lower DO levels. So pending the necessary calculations, I am happy to concede that air stones like the ones above are a good choice. Well pointed out :thumbup:
 
I like airstones for prevention of surface biofilm (works great) and vertical movement in the water column. I'm more ambivalent around oxygenation, but @Simon Cole have you factored in bubbles on the surface in addition to bubbles rising through the water column? In the Shrimphaus bubbles on the surface are much larger than 1 mm diameter and once on the surface count close to double since there is air on both sides of the bubble film (inside and out). Video below.
 
I would imagine that bubbles only form on the surface when there are oils and the like adhering them, but I suspect in most cases they would exhibit flat bottoms. The same bubbles might have been coated with oils when they previously migrated up the water column, but even then, from what I have read, many oils are diatomic-oxygen soluble.

I have been quite pleasantly surprised to find that that air stones have these benefits. We seem to have agreed that they have a great deal of value whether there is good surface agitation or not.
 
Hi all,
Simon Cole said:
So if we were to take these two points as integers and factor in the rate of air stone bubble acceleration and maximum velocity (speed) in pure water, then it would appear that even more air stone bubbles would be required if we wanted to match aquarium surface water air exchange.
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I think the point is that the <"rising bubbles are pretty efficient"> at enlarging the gas exchange surface area by water movement. This is a <"Czech air-lifter set-up">.



cheers Darrel
 
I have wondered about this with CO2 bubbles as well... how much CO2 in the water actually comes from the bubbles in the water column, vs. surface exchange from the layer of more-dense-than-air CO2 resting on top of the aquarium? I suspect quite a lot from the layered CO2 where you might expect a closed-top aquarium to more efficiently get CO2 into the water than an open-topped aquarium. The CO2 spray bar concept is a more controlled version of layered CO2 gas.
 
I can say for a fact, that prior to purchasing chillers, tropheus, which like high levels of O2, survived at 30C with 2 Eheim 400’s feeding 2 x 50mm round flat ceramic air stones, in 5x2x2 tanks, no matter how efficient or otherwise, the airstones raised to O2 level, enough to prevent fish loss, that occurred previously
I already had an Eheim 2217 (as a second filter) returning water through a venturi, this (in my tanks) was just not enough at 30C with tropheus
 
Hi all,
fredi said:
I can say for a fact, that prior to purchasing chillers, tropheus, which like high levels of O2, survived at 30C with 2 Eheim 400’s feeding 2 x 50mm round flat ceramic air stones, in 5x2x2 tanks, no matter how efficient or otherwise, the airstones raised to O2 level, enough to prevent fish loss, that occurred previously
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They definitely help.

Tropheus spp. would be demanding species to keep in <"dissolved oxygen terms"> (as well as aggression etc).

They are herbivorous, so plants are difficult and Lake Tanganyika has <"very stable parameters">. Rheophilic fish you can keep in a raceway, but with <"surge zone"> lacustrine species you need more of a reef tank set-up.

In the <"aquaculture"> / waste water industry they use <"EPDM diffusers"> (ethylene propylene diene (M-class), a synthetic rubber) these offer advantages over ceramic disc diffusers in that don't foul as easily and they can operate at lower air pressures.

cheers Darrel
 
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