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

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-

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

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

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.

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-

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

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

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.

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.