Where to position pipes on an aquarium

[Country joe]

I've been reading a book that advises inflow and outflow pipes should be opposite in a tank, I was going to put both on one side, would this be okay, I'm talking about a external filter, on a 70 litre tank.

 

[GaryE]

It's fine. Just try to adjust the outflow so that it goes away from the intake, to move the water around. You don't want only the freshly filtered water to be pulled up the intake.

 

[TwoTankAmin]

I have as many as 3 canister filters running on different tanks. I have always placed the intakes at the bootom of the tank at one end and the return at the other end. However, in my one high tech CO2 added plant tank, I placed the spraybar return vertically in the back corner on the opposite end. I also tend to modivy my output spraybar by drilling additional holes.

There are drilled at a 90° rotation from the pre-drilled ones. I drill a smaller diameter hole. I do this for two reasons. The first is to reduce the flow rate from the normal holes. This does not reucde the turnover rate of the filter, what it does is to spread it pout which lowers the output rate from any one hole. But it does another important thing which is to redirect tome of the output. Most of the flow is directed across the surface of the water so it agitates the surface a bit but then another amount of the return is directed downward.

My feeling is the way I do things creates better overall circulation in the tank. I also normally use multiple filters on tanks. Only the high tech p,anted tank did not use a second filter. But that was because I wanted to minimize CO@ loss to surface agitation. I have a 75 gal. with both a canister and an Aquaclear 300 (70) and the 150 has an Aquaclear 500 (110) and a H.O.T. Magnum on it. All the canisters are Eheim Pro II 2026 models.

As always this is just how I do things and not the only, nor necessarily, the best way.

 

[Uberhoust]

Most HOBs manage to work with the intake and outlet on the same side of the tank. I am sure one can get it to work with a canister as well. The flow on my canister will easily push the water to the far side of the tank and from there it will flow back if that is where the intake is. My canister is setup on opposite sides of the tank, but I wouldn't hesitate to put them both on the same side if the layout made that orientation better. Keeping the hoses to one side can make it easier to hide them, also overall your hoses could be shorter which improves the performance on the filter.

 

[TwoTankAmin]

But most HOBs do not involve hoses for either intake or return. This makes it a bit difficult to move them around. The only options we have is how deeply we place the intake and where we chose to hang the filter. We can add intake tubes to extend the length beyon one tube

On a number of tanks I have used two HOBs. I place them on opposite ands of the tank and I then use different uptake lengths. One filter has a single intake tube while the other has multiple tubes. I want one of the two intake points to be much closer to the bottom of the tank. I even have a tank or two using a pair of Aquaclears where one of them has three extension tubes on the intake.

Head is a greater slower of the return capability than the horizontal length. Unless a filter has a control over the power of the motor, there is only one speed. I have never seen a filter with a variable motor speed. All the ones which allow for control of flow do so after the motor/impeller not before it.

And let's not forget that most filtersd perfom multiple functing in a tank, there are no limited to just providing a place for the media where the bacteria which actually do the filtering, to live. To do so this the filter moves water though itself. But, a filter may also be toe sole device on a tank which create surface agitation and any amount of current in a tank. A hang on filter will do this even when there is no media in it and thus almost no biological filtration.

There is a reason the flow control is after the motor. If one impedes the amount of water coming into the part of the motor that actually moves the water, there is a risk it will damage the motor if insufficient water is going through it. An Aquaclear is a perfect example. Its flow control works by moving the intake U-tube off the center of the motor's output. The impeller speed does not change. The amount of water inside the body of the filter does not change because even though the intake is slower. the volume of water in the body of the filter does not drop in any way that prevents the motor from having a full load of water in it.

In any canister with flow control it should be slowing both the intake and return flow evenly balanced. And that insures the water volume inside the canister remains constant. Wwhich means the motor should never have air in it.

Let's consider the basic filtration optione offered to hobbyists. The cheapest form of filtration is air driven. The next cheapest are hang-on filters, then would be canisters and finally there are the sunp systems. The size and cost of all of these increases each step of the way. Air driven systems can be large and used on multiple tanks with a single air pump. But, it is the air power moving the water not a water pump.

There are two things which are mostly responsible for the flow rates in any filter. One is the diameter of the tubing and the other is the power of the filter motor. A lot of one's choice of filtration depends upon the volume of water involved. We will never see huge tanks filtered by HOBs.

There is one basic difference between how a hang-on and how a canister or sump system work. The HOB needs it's motor to suck in the water and then it relies on gravity, from an overflow, to return that water to a tank. Canisters and sumps rely on gravity to intake the water and then for the motor to pump it out and back to the tank. The intake is a siphon on such filters.