Damn, thats well put.
water_baby83;229082; said:Actually, it's quite easy to go beyond atmospheric equilibrium. When the total pressure of all the gases in water reaches above the ambient atmospheric pressure at the surface, supersaturation happens. The effect of excessive super saturation has been documented, and if it goes beyond the safe levels, massive fish disease/death can be the result. As zoodiver said, malfunctions in water pumps used in re-circulatory systems can cause air entrainment if a leak occurs near the intake of the pump.(this is basically lots and lots and lots of bubbles) I will let him go into that further, simply because I dont feel like it,lol. But I did want to point out a problem (side effect) of under saturation, which wasn't yet discussed, and can have just as bad an effect as over(super) saturation. (deep breath), OK, I might get carried away here, and if chemistry is not your thing, turn away now.....lol............
The composition of water is extremely important for aquatic life. Fish or plants need water not only for respiration but also for the transport of nutrients and waste materials. Though relatively high levels of oxygen saturation are acceptable, and in many cases encouraged, there can be serious down falls when it comes to under saturating your tank.Your PH level is one of the most important indicators of water quality in your tank, and also the first to be thrown out of whack from super saturation or on the flip side under saturation.The acidity of water (pH) is an overall effect of all dissolved ions on the electro-negativity of water. In the "blaa blaa" of chemistry;----- acidic water tends to take free electrons whereas basic water tends to give. Most bacterial processes take place around the neutral pH levels ranging from 6.5 to 7.5. This means, bacterial recycling(bio-filtration) is most effective on the close vicinity of neutral pH levels. Higher and lower pH levels diminish the speed of bacterial recycling. When your pH levels drop due to under saturation, Nitrite is more toxic because a higher proportion of nitrite (NO2-) is converted to toxic nitrous acid (HNO2). Carbonate hardness (KH) plays a central buffer role here in keeping the acidity stable. But I don't feel like explaining that right now either,. Dissolved carbon-dioxide (CO2) is one of the most important molecules in an aquatic system that determines acidity (pH). Higher concentrations of dissolved CO2 gas increases acidity (hence reduces pH) because CO2 is partially converted to carbonic acid in water. The following two-way chemical equation explains the equilibrium between CO2 and carbonic acid H2CO3:
CO2 + H20 <--> H2CO3 ( = H+"positive" + HCO3- "negative")
To put that in a not so boring way -- If we add more CO2 into the water the chemical equilibrium point will shift to the right; more CO2 will be converted into H2CO3 and acidity will increase (pH will drop) as a consequence. If dissolved CO2 is dissipated into air by e.g. aeration or heating the equilibrium point will shift to the left; some of the carbonic acid will be converted back to CO2 to replace the dissipated amount and acidity will decrease (pH will rise) as a result.
How is this cause by under saturation?
Fish take dissolved oxygen gas through their gills and give out CO2 as a waste product of respiration. Except for some adapted species like mud skippers and some labyrinth fish like betta which can utilize atmospheric oxygen most fish depend on the dissolved oxygen gas in water. Oxygen is in a much shorter supply in water than in the air: A liter of air contains about 260mg oxygen whereas a liter of freshwater contains a maximum of 8.5mg dissolved oxygen (25°C at sea level), about 30 times less. Aerobic recycling bacteria that colonize in filter and all kinds of surfaces can also contribute to loss of oxygen. Photosynthesis of water plants, and direct diffusions from atmosphere which is further utelized by surface disturbances, and over-all circulation, are two ways to reach near levels of saturation. Oxygen levels should not be allowed to drop values below 3 mg/liter. And a vigorous water circulation is not necessary; it may even be harmful to plants because it deprives them of their most important food: Dissolved CO2.
Saturation -which is a kind of equilibrium state- is reached if the amount of oxygen diffusing into the water directly from the atmosphere is equal to the amount diffusing out of the water into the atmosphere. Aeration accelerates the gas exchange in both directions; thus, saturation is reached faster if we aerate water. If there are oxygen producers such as plants in water the levels of dissolved oxygen may well exceed saturation levels. This situation is called super saturation. But We already know that, lol. Aside from chemical changes due to under/super saturation, a variety of ailments can arise as well for either condition. This makes it even more frustrating when trying to keep the balance. It's like tight rope walking, either way you turn, it can spell disaster. But OMG, I just realised I totaly went off on a spree there, and probably bored the hell out of most of you -- sorry!! OK, I will stop, but I just want to say, that there is much more to this than what is here (yeah i know -- MORE??). If I had to suggest one SIMPLE way of monitoring your saturation levels accuratly, I would suggest getting a dissolved gas sensor. They monitor saturation levels along with nitrite, some do more. But yeah, my brain hurts now, lol, so I am shutting up.
--EMI
