Biofilm and surface agitation and floating plants

[imw]

I was just thinking about the above.

Surface agitation will aid gas exchange and in my S/W days it was a fairly important thing to do.

When I look at F/W tanks I note there does not seem to be much agitation at the surface of the water, is not something we need to consider ?

I note in my tank some biofilm and I have some floating plants, so assumed if I increased the surface agitation the floating plants would not enjoy it.

Some guidance would be appreciated.

Thank you

 

[Bruce Leyland-Jones]

I was just thinking about the above.

Surface agitation will aid gas exchange and in my S/W days it was a fairly important thing to do.

When I look at F/W tanks I note there does not seem to be much agitation at the surface of the water, is not something we need to consider ?

I note in my tank some biofilm and I have some floating plants, so assumed if I increased the surface agitation the floating plants would not enjoy it.

Some guidance would be appreciated.

Thank you

We are now more aware of sensible stocking levels, (hopefully) matching our fish populations to the surface area, (amongst other things), so perhaps agitation of the surface now gets less mention.
We're also more sensitive to the needs of the fish, with regards water movement. Community tanks would've held all manner of fish, some of whom would've been unsettled in agitated water. I'm thinking community tanks today take that into account and surface agitation is promoted less as a consequence.
I've also noticed an apparent decrease in the use of airstones, except in emergencies.
I remember aeration was considered an essential element to any successful aquarium and, (awful bubbling toys aside), there was a wide range of airstones and even air 'curtains'. I'm thinking that today many dislike the noise, or view a constant stream of bubbles is unnatural and then, of course, there's the aforementioned detail about some fish preferring quieter spaces.

Personally, I still view surface agitation as an essential componant of my own watery ecosystem, facilitating good gas exchange throughout, with airstones running and my filter outlet stirring the surface. (I even have a venturi running).
I have no issue with the 'unnatural' feel of airstones running, knowing that real streams and rivers are usually in constant flow (and subsequent noise), even with bubbles included.

I have surface plants and they are moving around quite 'happily'* with the current. Unlike in a stream, they are in no danger of being washed away. If I wanted to, I could encircle them in a loop of airpipe and attach said loop to the side of the tank with a handy sucker.

*Obviously, plants don't have emotions and 'enjoyment' may not be a feature of their existence, but they do need good light, the right temperatures and access to the right nutrients, gaseous and otherwise. With these ingredients, they'll be 'happy'.

 

[imw]

We are now more aware of sensible stocking levels, (hopefully) matching our fish populations to the surface area, (amongst other things), so perhaps agitation of the surface now gets less mention.
We're also more sensitive to the needs of the fish, with regards water movement. Community tanks would've held all manner of fish, some of whom would've been unsettled in agitated water. I'm thinking community tanks today take that into account and surface agitation is promoted less as a consequence.
I've also noticed an apparent decrease in the use of airstones, except in emergencies.
I remember aeration was considered an essential element to any successful aquarium and, (awful bubbling toys aside), there was a wide range of airstones and even air 'curtains'. I'm thinking that today many dislike the noise, or view a constant stream of bubbles is unnatural and then, of course, there's the aforementioned detail about some fish preferring quieter spaces.

Personally, I still view surface agitation as an essential componant of my own watery ecosystem, facilitating good gas exchange throughout, with airstones running and my filter outlet stirring the surface. (I even have a venturi running).
I have no issue with the 'unnatural' feel of airstones running, knowing that real streams and rivers are usually in constant flow (and subsequent noise), even with bubbles included.

I have surface plants and they are moving around quite 'happily'* with the current. Unlike in a stream, they are in no danger of being washed away. If I wanted to, I could encircle them in a loop of airpipe and attach said loop to the side of the tank with a handy sucker.

*Obviously, plants don't have emotions and 'enjoyment' may not be a feature of their existence, but they do need good light, the right temperatures and access to the right nutrients, gaseous and otherwise. With these ingredients, they'll be 'happy'.

Thank you Bruce for the input.

ATB

 

[itiwhetu]

I like the idea of an air stone. I always say that if you put an air stone on a tank it doubles the surface area therefore doubles the capacity of the tank. Without an air stone the surface of the tank is like a sheet of glass put an air stone in your tank and the surface looks like a piece of corrugated iron. We are to pre occupied with looking at substrate to bother about what happens at the top of the tank.

 

[Myraan]

My theory is when fish gasp at the surface because of nitrite poisoning, years ago we would assume oxygen was low. Today we get a test kit kit out to rule out nitrite issues. I suppose the two issues are linked as the filter bacteria need an oxygen supply.

Then we as aquarists like to confuse issues by filling our tanks with anabaptids and cories.

 

[Bruce Leyland-Jones]

I like the idea of an air stone. I always say that if you put an air stone on a tank it doubles the surface area therefore doubles the capacity of the tank.

I remember some aquarists saying exactly that, long ago...and then when their air pump failed, they soon had a load of dead and dying fish, gasping for oxygen at the surface. I quickly learned to have at least one spare air pump tucked away somewhere and that's I habit I've retained ever since.

 

[Byron]

The gas exchange that occurs at the surface is very important to the fish, and by all accounts the plants too. I do not have the statistics, but I believe others have noted that surface disturbance is much more effective that any "bubbling."

I have live plants in my tanks. We used to read that too much surface disturbance would drive off needed CO2, and while this is certainly true, it is also true that insufficient surface disturbance will be detrimental to both plants and fish. A few years ago, planted tank authors were beginning to advocate for some surface disturbance as not being detrimental to plants but the exact opposite.

In my planted 70g (4-feet/120 cm length) Corydoras tank, I had the Eheim canister filter return at one end. I used the spray bar to push the water down the end glass and thus across the bottom, so there was very minimal surface disturbance. I happened to be sitting in front of the tank when the tank light came on one morning, and noticed all the cories respirating faster than normal. Instinctively I removed the spray bar and adjusted the filter return spout so that it rippled the surface at that end. Never saw the cory issue again. I assumed the plants during the darkness were respirating as they do, along with the fish, and the CO2 being produced by the decomposition of organics in the substrate, and this increase of CO2 at night was causing the reduction of oxygen available to the fish. The plants have not suffered, and the fish seem better.

Sometimes one has to delicately balance things. I frequently noted that many of the characins in my 5-foot planted tank remained at the opposite end of the tank where the current was much less than at the end under the filter return. I do not think this was accidental, but a clear case of the fish being more "comfortable" in quieter water.

 

[Bruce Leyland-Jones]

There's a lot of surface area in all of those bubbles and I believe that airstones facilitate the removal of gases as much as the absorption of gases.

 

[Myraan]

I could be wrong but I always understood the main point of bubbles was that they suck the water to the surface and mix gases between water and air that way. So a non bubbly filter return or circulation pump pointing sorta up will do a similar job. Having said that I quit using venturi on my old internal filter because it seemed to be increasing pH so I worried about the CO2 for the plants.... so maybe you are right about the bubbles surface area

 

[StevenF]

Plants in a fresh water environment help consume organic and nutrients which can make biofilms less of an issue in fresh water tanks. The plant also produce oxygen and reduce CO2 levels which is also good. In most salt water tanks there is often no sea weed to perform that function.

I have live plants in my tanks. We used to read that too much surface disturbance would drive off needed CO2, and while this is certainly true, it is also true that insufficient surface disturbance will be detrimental to both plants and fish.

Since the air always has CO2, lakes nd streams there always is some CO2 in the water. If you have excess CO2 increased surface agitation will Reduce the CO2 level. However if the CO2 level in the water is below equilibrium with Air CO2 levels the opposite happens. Increased airation will drive CO2 and oxygen levels into the water.

In high tech tanks with CO2 injection the easiest way to measure CO2 is to use a drop checker. However many don't know that a drop checker can only detect CO2 if the water has more CO2 than the air. So If you have too much agitation of the water surface a drop checker will read zero CO2 levels. Currently the atmosphere has about 410ppm of CO2 in it. For a drop checker to detect it you probably need a minimum CO2 level of about 450ppm.

Apparently if is difficult to accurately measure CO2 in water. You need to filter out all carbonates, minerals and organics first. And then you can determine CO2 levels by measuring PH of the water. Measuring the PH of the aquarium water doesn't work since the PH value is dominated by carbonates, metal hydroxides, and organic acids in the water.

Just a note that floating plants may not oxygenate the water. they mainly take in CO2 and release oxygen from the dry top side of the leaf. Generally surface agitation doesn't harm floating plants but it can reduce the amount of gas exchange with the air. Fo for floating plant it is best keep a barrier between the pump water outflow and the floating plants to prevent interfrearance with gas exchange..

 

[Bruce Leyland-Jones]

I could be wrong but I always understood the main point of bubbles was that they suck the water to the surface and mix gases between water and air that way. So a non bubbly filter return or circulation pump pointing sorta up will do a similar job. Having said that I quit using venturi on my old internal filter because it seemed to be increasing pH so I worried about the CO2 for the plants.... so maybe you are right about the bubbles surface area

Not so much a 'maybe' as a fact of physics and gaseous exchange.
The flow of water created by a bubble stream, however, is how many older filters, including the under gravel type, were powered. Even today, you can buy the simplest of filters that are run by an airpump, where air is pumped into the filter and the bubbles rise to the surface of the tank, drawing water up with them. Whilst this flow of water isn't particularly strong, it is strong enough to pull water through the filter.

 

[Bruce Leyland-Jones]

Just a note that floating plants may not oxygenate the water. they mainly take in CO2 and release oxygen from the dry top side of the leaf. Generally surface agitation doesn't harm floating plants but it can reduce the amount of gas exchange with the air. Fo for floating plant it is best keep a barrier between the pump water outflow and the floating plants to prevent interfrearance with gas exchange..

As I understood it, the real purpose of floating plants is their superb ability to take up nitrates from the water's nitrogen cycle.

 

[Byron]

As I understood it, the real purpose of floating plants is their superb ability to take up nitrates from the water's nitrogen cycle.

Just so you know, floating plants do not take up nitrates. They take up ammonia/ammonium as their preferred source of nitrogen, and because they do this faster than the nitrifying bacteria/archaea do, plants out-compete the nitrifiers. That means there is no nitrite (from the plants I mean), and thus no nitrate...so there is in the end lower nitrates. Some ammonia/ammonium will get to the Nitrosomonas bacteria, and continue the "cycle" bit, but you won't be able to measure this ammonia or nitrite with our hobby test kits, the volumes are so minimal.

Very few aquatic plant species actually take up nitrate. You can see the studies referenced in Diana Walstad's book. The vast majority, enough to be able to say "all" with minimal reservation, use ammonia/ammonium. They only turn to nitrate as a last resort if ammonia/ammonium is not adequate in balance with other nutrients and light. When these plants do take up nitrate, they must use considerable energy to convert nitrate back into ammonium, so they don't do this unless forced into it. Aquatic plants use the N from ammonium—not nitrates—to produce their amino acids and proteins.

Floating plants have the aerial advantage when it comes to taking up CO2 because it is about four times faster from air than water. They can take up an incredible amount of ammonia/ammonium, and store it. Often termed "ammonia sinks" for this very reason.