Mid-tank or bottom intake overflow system

[desm0nds]

Hi everyone,

Pardon me for the long story but i need to present the background story first la. I am sure that aglae on the tank's wall is rather common among us. Despite having high water flowrate, low nitrate level, strong water current, lighting intensity and exposure period controlling etc. Still, we will have aglae growing on the wall. (If there is someone who does not have this problem, please please share with us how to achieve this.) When we scrub away the aglae, the remains tend to "swim" around in the tank. It doesn't float to the surface and as a result, they doesnt get suck into a typical surface intake overflow system. Quite often, they settled down on the sandbed, rocks or even back on the wall again. End result, aglaed wall, rock and sandbed. Yucks.

I am thinking if we can have a mid-tank or bottom intake, we could remove these "waste" more effectively and more efficiently?

I have tried incorporating a mid-tank intank to my existing surface intake oveflow system but it doesnt work. Somehow the balancing between the pump rate and the overflow rate is being disturbed. Having a ball-valve installed to control the flowrate doesnt work either.

Anyone has a mid-tank or bottom intake overflow system in your tank setup? There are a lot of surface intake overflow system design being posted here in the forum, but none is on mid-tank or bottom intake overflow system design.

Surface intake overflow is good in surface skimming as well as simpler to design as balancing the overflow rate and the pump rate is achieved automatically. But what it lack here is the effectiveness of the "waste" clearance.

Hope that someone out there has a solution to this... Very much appreciated.

[Achilles Tang]

IMO, its very hard to make a mid or bottom intake for the overflow system and expect it to work well. Note the word 'overflow'. It means water has to go over the lid of the chamber, otherwise, a 'midflow' chamber or 'underflow' chamber would be common.

Waste? I am assuming you mean detritus? These can only be effectively removed from the water column into the overflow and into the sump where the mechanical filtration could help filter out/export these waste material by the action of good water circulation.

Good water circulation is defined as random flow of water currents such that there are no dead spots.

Its a challenge to give good water circulation to every spot in our tanks but it has been a lot easier these couple of year with the introduction of better wave-making gadgets such as the Tunze Streams, Wave2k etc.

Powerheads have limited use.

[ryz]

water flow in thru bottom, inside overflow box make another box and the only exit to the sump is thru this box. So the water taken in from the bottom will have to travel to the top of this box and overflow into it. So although the water is taken in from the bottom, it can still function like a standard overflow box.

[Achilles Tang]

Hmmm... yeah... saw this design before... This design may work for freshwater tanks but not really applicable for marine tanks where you can't use this design if you want to incorporate a DSB.

Anyway, I don't think the 'suction' through the bottom slot is good enough to move that much water into the chamber that has to travel upwards and then over the lid. The question is... what force is forcing water into bottom slot and against gravity to go over the lid?

The water will simply rise until it moves over the overflow lid and gravity flow downwards at a faster rate.

[ryz]

yea will work like an overflow box I suppose. the tank wqterlevel has to exceed the glass box inside the box before it will overflow in.. However the water entering this box will be taken in from the bottom of the ooverflow box. The water won't rise untill it moves over the overflow box lid. as the water level in the overflow compartment will be the same as the water level in the main tank since there are openings at the bottom of the overflow box. SO when return pump pumps water to main tank, overall water level rise, the water in the overflow box will overflow into the custom glass box and into sump...

Maybe if wanna incorporate DSB the intake can be made in the middle? like 6 inches from the bottom so can have like 5" - 6" of DSB?

[Achilles Tang]

The limitations of such bottom or midwater slots is that you probably cannot use these with higher capacity pumps for faster overall system water turnover to the sump unless you can work out the slot dimensions maximum water intake capacity or you could maybe see a potential flooding happening! At the best case scenario, water will go over the lid like an ordinary overflow but that would probably nullify the midwater slot intake somehow.

Just my reasoning....

[ryz]

hmm... I have a tank using that system.. I modified it... using 5000l/h pump.. it will never overflow the lid as once the water level reaches over the overflow chamber, it will overflow in. the water level in the overflow box will be the same as in the main tank.. It is like inserting a OC tube vertically downwards into a pool of water. the water level in the PVC tube will be same as in the water. atmospheric pressure will force the water up the tube and the air out of the PVC tube.

[ryz]

as can be seen from this picture, the water overflows into the intake chamber thru the overflow box partitioned..

[ryz]

as u can see the water level here is maintained well below the overflow chamber's top.

Think about it. If you just build a compartment in a normal tank, not an overflow box, but just a compartment at the corner of the tank, with many holes near the bottom of this compartment. the water level in the main tank will be the same as in this compartment due to atmosapheric pressure.

[Achilles Tang]

Hmmm... do you feel you lack the benefit of surface skimming with a mid-level water intake?

[ryz]

hmm... Never thought much about that.. dun have anything accumulating at the surface as of yet. Might try to find a way to skim the surface as well.. any suggestions?

[Achilles Tang]

Marine tanks benefit a lot from surface skimming as that will improve the oxygen diffusion, not to mention removal of the oils that build up through feeding, coral slime, foam or even insects that land on the water surface.

I don't know how you are going to skim the surface without an overflow coz your water intake is similar to those reefers who use canisters without the benefit of a extra surface skimmer attachment.

I think the only way you can overcome such problems is to 'churn' the water surface with a powerhead such that it is never 'still'.

[ryz]

hmm... anyway tts my planted tank my marine tank using the normal overflow box.. I might still add a powerhead to create turbulance at the surface though.. Oxygen diffusion or rate of oxygen dissolving in water?

[Achilles Tang]

Planted tank???

That's even worse!! The OIL on the surface of planted tanks is even thicker than marine tanks!!! I use to drop tissue paper flat on the surface just to extract the oil!!

[Golden Tooth]

I'm using the bottom intake overflow. Ard 1"-2" hole was drilled at slightly higher than the water overflow level for the surface. I'm running a barebottom tank. IMHO it all depends on ur water circulation n amount of water returned from the sump.

[desm0nds]

Hi guys, thanks for all the suggestion and comments. Well seems like we can't come to any conclusion yet.

Currently this is what I have been using in my tank. Suppose to work with both the surface skimmer and the mid-tank intank. The mid-intake proof to be very effective in ###### in the debries. But ... sigh... I can nver achieve a perfect balance between the overflow rate and the return pump rate. (despite using the ball valve to control the flow).

The idea is there but in practise, it failed. And I am hoping that someone out there could at least provide an alternative solution or maybe even modified on this system.

The box within the overflow box could not be used here as you can see that I do not have a "box" in this design.

[ryz]

no build up of oil at surface as of yet..

[minsmarine]

Before I have my iBox ( Can't drill the hole in my main tank casue already estiblished b4 decided to go for sump ), I use very simple water inlet. something like your but not complicated. I only have 1 inlet and using 15mm pipe to drain down to sump and pumped back with 2,800L/hrs ( Resun SP6000 ). I have valves in both intake and return. Managed to balance by adjusting both ( if slow in, open more in ). Sound like st***d. However it worked with some nightmare. Need to have a lot space for the water ( if pump fail ).

Good thing was I used that for 2 weeks and it doesn't fail. Only thing is need to adjust almost every alternative day.

[surfedelic]

If there is oil on the surface - I think it is still easier to maintain the surface then maintained the sand bed. Might be trying out this underflow concept.

[desm0nds]

Good thing was I used that for 2 weeks and it doesn't fail. Only thing is need to adjust almost every alternative day.

This is what I meant by not able to achieve a perfect balance. I too used to make the adjustment every alternate day. Very sianz... That's why decided to use only surface intake. But create another problem as mentioned earlier.

no build up of oil at surface as of yet..

If water is not being suck into from the surface, surely there will be oil built up sooner or later. As I have tried using only the mid-tank intake, weeks after, i can see a layer of oil on the surface. You might want to reconsider on your design?

[minsmarine]

This is what I meant by not able to achieve a perfect balance. I too used to make the adjustment every alternate day. Very sianz... That's why decided to use only surface intake. But create another problem as mentioned earlier.

Well, if we don't think about intake for sump, than we can do it as closed loop.

I am going to use in my closed loop with my intake than no need to adjust.