An example and series of questions about plants, algae and current velocities

[Tom Barr]

Current is perhaps one of the least discussed topics for advanced and beginning folks in plant forums/books.

The effects can be seen in both FW and marine systems.
Tide pools are pounded mercilessly by intense wave action and have pristine macro algae, when waves are not intense, and the the water stagnates, these pools become wrought with Cyano and diatom blooms.

Likewise, in FW rivers and streams, we can see a very similar pattern.

This is a small irrigation ditch that we have been treating for Hydrilla.
The current is about 1-2mph in the middle, not algae, clean plants, along the edge, the current is very slow, non measurable.

You can see the differences.
The water, light, sediment etc are the same.

So.......put your thinking caps on..........what is different that you can think of?
How do those things influence plant and algae growth here?

Suppose we increased current to say 5-10-20mphs?
Do you trhink the plants would do even better?
Worse?

Why?

You should see a bell shaped curve with respect to current, good plant growth without algae.

At low velocities, lots of algae, medium velocities, 0.5-3mph, good plant growth, few algae species, above 2-3mph, more algae on some plant species and fragmentation/mechanical destruction of plants-> more thread type/stream algae etc.

Surprising?
No, not really.

But few planted aquarists even consider any of this for some reason.



Regards,
Tom Barr

 

[FacePlanted]

This is really good. Current, circulation, and flow patterns are something that I wish I would see discussed way more of on these types of forums. I have had questions in the past when I was building my filter inflows and outflows. I needed to know how to get the best circulation/flow pattern in the tank. Whether I needed more outlets/inlets, use a spraybar, high, low, left to right, top to bottom, where to place the inlet, flow rates & patterns, etc. Everyone says to increase circulation to remedy certain problems, but no one really goes into detail on how to do it, other than saying, "add a powerhead."

The need for good flow and circulation is obvious, but how to provide this in a tank really isn't. I would love to know where I could find a discussion on these specifics.

-Mike B-

 

[yme]

very important post imo...
I used to (almost) CO2 poison my fish and still got algae growing on plants and grass etc etc.
I decided that I wanted to have some fish anyway, thus upped the pH by 0.3 points. the difference was clear on the DIY drop checker (darker green).
Because all the macro's and micro's are takencare for, the only other remaining factor is current. I put in an extra powerhead with the outlet directed directly against the glass. for more than a week I let this setup run. No algae was observed on the glass within 20 cm from the powerhead outlet. plants seemed to pearl more and I think that the water is clearer.

greets,

yme

 

[swylie]

The flow doesn't change the sediment in a significant way?

 

[Carissa]

The only place I am still growing a colony of bga is on the outflow from my hob filter. I'm not sure why because I thought that poor circulation usually is better for bga growth.

 

[FacePlanted]

could you describe the direction that the water is circulating? where the outlets and powerhead is pointed, and where the intake is? ie: does the water flow in a circle from left to right, top to bottom, or 2 outlets pointing towards eachother making 2 circle flow patterns with the intake placed maybe in the middle?
Are any of these combinations/setups better than any other?

-mike b-

 

[Tom Barr]

The need for good flow and circulation is obvious, but how to provide this in a tank really isn't. I would love to know where I could find a discussion on these specifics.

-Mike B-

That's a large part of this post, it's partly some of an old BR newsletter as well.
I just saw a nice example of the concept from a system in an irrigation ditch(hardly natural!).

Regards,
Tom Barr

 

[Joetee]

This is so interesting. Just last night I was laying there in bed trying to go to sleep but could not help thinking of my tank. ( Obsessed? Yes ). My thoughts were on circulation. I was thinking of a way to build something small that would hide easily like a clear pipe that fit tightly against the glass that went all the way around the tank either at the top, bottom, or both, with one water inlet from the filter. At about 2 inches from each corner of the tank have a hole drill with maybe a small tube pointed in the correct direction to aim the water spray to cause it to circulate around the tank like bath tub water circles around the tub when you pull up the plug. This can be either at the top of the tank or hidden under the substrate with only the small tubes showing. Then I thought of putting my water return tube to the filter down the back wall to the bottom of the glass and coming under the substrate and then up just above the substrate in the middle of the tank. All hidden with plants etc.
This is like when you add your dry ferts into a jug with water and give them a stir and then stop and watch, you notice the particles settling in the center bottom of the jug. This would be where your tank debre would be sucked up to your filter.
Possibly all glass tubing. The correct size holes drilled etc.
Quite the concept. I wonder if it would work and be affordable to the average hobbist?
Any thoughts?
Joe

 

[VaughnH]

The first problem that comes to mind is that a nicely aquascaped aquarium is much, much different from a jug or bathtub or even an empty aquarium. The mass of plants will disturb any water circulation, making the circular vortex you described disappear. I think that is the biggest problem we face with water circulation - we set up the circulation with a nearly empty tank, when we first plant everything, but when it all grows out the circulation changes drastically. I'm not real sure how one maintains good circulation with a tank full of plants, without having a few dead zones someplace.

 

[Joetee]

Well what I see is, the water even in near dead spots, still should have just a little movement at least. As the fish etc move around and disturb debre, it should still make its way down stream. Slowly yes, but still should move toward the water suck tube. Ferts and nutrients need good movement. I think the trick is to get the nutrients, C02, debre, etc, to move fast enough but not to fast, to make a difference in your tank in regards to algae, cleanliness, and good plant growth.
I have one canister filter and one power head but yet still don't get the movement that I would like to have without blowing my plants over. It seems to me that the more water sources to move water, the less dead spots we will have. But at the same time we don't want a tank all cluttered up with equipment. This was my idea to try and get as much water movement as I can without blowing my plants over and not have a cluttered tank.

 

[Carissa]

could you describe the direction that the water is circulating? where the outlets and powerhead is pointed, and where the intake is? ie: does the water flow in a circle from left to right, top to bottom, or 2 outlets pointing towards eachother making 2 circle flow patterns with the intake placed maybe in the middle?
Are any of these combinations/setups better than any other?

-mike b-

HOB = hang on back filter
It's just the place where the water is overflowing from the filter into the tank. I think maybe it's because it's really close to the lighting. Still weird though.

 

[Tom Barr]

Folks get all sorts of algae on the filter and in the tubes.
Hard to clean in those spots, and fish do not bother the alga there.
You often can see BGA along/below the gravel line and the glass

Regards,
Tom Barr

 

[FacePlanted]

The HOB "waterfall" and the filter tubes is where I also saw the algae, crud, BGA first appear in my old tank, and later just below the gravel-along the glass, too.

Joetee:
I too try to get sort of a circular "swirl" in my tank. I have 2 inlets and 2 outlets for my filter. One of the outlets is a flo-pipe (lily-pipe knockoff) at the top-back of the right side of the tank blowing the water across the top from the right to the left. The other outlet is in the front-left corner of the tank, but about 1/2 - 2/3 the way down below the water. It is blowing water across my co2 diffuser in the bottom half of the front of the tank from left to right. I figure this gives a :general: circular flow pattern in my tank, but one outlet creates a vertical "flow circle" while the other creates a horizontal one. One of the filter intakes is a regular "flo-pipe" intake and is on the back glass in the right corner. The second intake is a Hagen surface skimmer that takes water off the surface, as well as from near the bottom of the tank. This is located on the back glass in the center of the tank. It does a great job of keeping the scum off the water's surface, and really helps with o2 exchange at night.

This does a good job at blowing co2 mist across the HC foreground, and gives a fairly good mix of co2 enriched water through the whole tank, but the mist really doesn't get dispersed to the plants along the back-half of the tank.
In addition, I do not think that the placement of the intakes really compliments, or works to the benefit of, the outlets.

I feel that one of the dead spots in my tank is exactly the place you talk about--right in the very center of the tank. Maybe this would be a good place to put the intake, but that hardly seems possible--at least in my setup I would have no way of doing this. The other dead spots in my setup would possibly be in the back left corner and the far right side (maybe in the back, under the flopipe outlet?). The corners that are opposite the corners with the outlets?

I dont think I will really be able to tell until I am able to take out the small internal filter that I had to use in the setup of the tank to help with the filtration until the big filter cycled. I believe this small internal filter is disrupting the overall flow pattern of the main filter outlets.

In any case, this is about the best I could think up at the time. It is certainly an improvement from my old setup, but probably far from perfect.

tank is a 29gal. using a quietone 3000 inline pump-780gph at 0 head-10ft. max head--- with a single size AF-94 pentair aquatics lifeguard pressurised mechanical combo filter. (and a temporary small penn-plax 10gal internal filter)

Any comments, or suggestions for improvement are appreciated.

Thanks for putting up with my wordy posts,
-Mike B-

 

[FacePlanted]

Duh....in such a lengthy answer I forgot my original reason for writing.

From what I gather, the necessary flow pattern is basically different for each tank.
It depends on the hardscape, type and size of the plants, the equipment you have available to work with, etc.

The best method is just trial and error....seeing what works. I'm sure experience comes into play, like it does anything, but each tank seems to be unique in various aspects and that is what keeps a plain and simple answer from popping up.

Thanks for listening, (reading)
-mike b-

 

[FacePlanted]

double post

 

[Joetee]

FacePlanted,

I recently changed my tank a bit and it did make a great difference. I have my water return from the filter up high in the back right pointing a little towards the right side which took care of the front right dead spot and still causes the water to circulate. I put my water suction tube down near the bottom rear right. I put my power head in the back left pointing water along the back of the tank towards the back right which helps push debre to be sucked up into the filter. The water along the front of the tank does have movement but not to much as to take away from it beauty. I can see the leaves moving slightly and debre moving a long the gravel. After running it this way for a week I noticed my tank much cleaner now. I do not vacuum my tank either. I use a turkey baster every once in a while to swish the water around and move debre towards to suction tube. Used to be a lot of debre kicking up but not now, very little.
Like you said, every tank is different. The only thing I had to do is make sure my plants were not all bunched up against the glass in the back and sides. A 1 to 2 inch clearence is plenty of room for the water to get through and creat the current necissary to move debre.

 

[VaughnH]

I wonder if anyone has tried making a custom filter inlet pipe that goes down the back under the substrate, then forward to the center of the tank. Then, I wonder if that would work any better than where the inlet usually is, at the back in a corner.

In my case I am thinking about putting my powerhead back in the tank with the flow going across the back from corner to corner. That might create a better circular flow in the tank.

 

[Tom Barr]

I think you need to play with things a bit here to get the best dispersion for a given design.

I use a 200gph filter on my 20 gallon tank, and simple have the in/out at the same place, but the outflow at one corner blasting along the surface about 1" down and then at slight downward direction so that I get a decent swirl around the tank.

Some surface ripple but never enough to break the surface.
I'll get a little algae if the flow reduced by about 1/2 or more(I use a prefilter sponge on the inlet and it can get clogged).

So I keep that nice and clean.

Regards,
Tom Barr


Regards,
Tom Barr

 

[Joetee]

Tom Barr,

I'm glade you brought up circulation because it seems like good circulation is the secret to a nice looking tank with good plant growth, good C02 levels dispersed around our tanks, good fert movements, and less algae issues.
Hopefully we'll get more people replying here with some of there hints, tricks, things that worked and did not. Reading how some has set up their tanks can give us idea's to try and then report back on there findings.

 

[Tom Barr]

It's difficult to describe flow in "words" on the web in 3D.

As plants grow in, they dramatically reduce flow rates around them, generally about 90% less. This is true in lakes, in streams/rivers etc.
It's fairly robust.

If you think a reduction of 90% in flow around a plant has no influence, well, you are a brick shy

Steve Dixon and I talked so much about this about 10 years ago we went nuts.
90% can make a massive difference in exchange rates and diatoms/epiphytes etc blocking the leaves. Then there is light and plant - plant competitive interactions.

Some plants are better at survival when the weeds grow in well and other plants are not.

If you kept the same group pruned, the effect would not be noted, but it has nothing to do with "allelochemicals". Many think allelopathic chemicals with algae/plants, but plant plant examples are far more common in the research, but it's still unfounded for aquatics.

Much more likely simple competition for resources that become much more limiting as flow rates and light and CO2 and other nutrients become scarce

You can see the difference by simply approach it from a flow and maintaining the same biomass/flow patterns.

Prune and ye shall see the light!
But some clowns want to blame nutrients for everything or their dosing methods.

Plant horticulture has many fassets.
Aquatics have even more issues.

We should not assuem too much or think ourselves too smart, we are quite feeble minded

At least I am!
And I must re evaluate everything a few times and keep coming back to some rather simple ideas and look at them from the ground up.

By starting with a simple concept and beating it up from every angle, we can get a better understanding. I've done this several times with CO2, light, nutrients, water changes, algae, fish etc. I do learn something new everytime also.

Flow, current etc is quite a big topic in the academic area.

Regards,
Tom Barr






Regards,
Tom Barr