# [Wet Thumb Forum]-Bubles from filter



## Rumpled (Jun 23, 2003)

Hi there, well this has me completely stumped. both my filters (Eheim cannisters 2026 pro2) after lights on until lights off are producing little bubbles in bursts at 10-15minutes.

At first I thought that I had a leak in the sytem. So I went to the expense of replacing all the seals, checked for alignment of the baskets, one of which is not real good.

Then the same thing kept happening.

So this morning I waited for the lights to come one and watched. For about 1 1/2 hours nothing, no bubbles. Then slowly bubbles started. By about 3 hours after lights on the same thing was full on. Burst of bubbles every ten to fifteen minutes.

I think it might be plants pearling close to the intake. I currently have 2.8 watts per gallon, Dupla CO2 sytem (co2 at 22ppm), and heavily planted.

Am I right, has anyone else seen this, and what can I do?

Rumple

Beware of the hand that feeds you!!


----------



## Rumpled (Jun 23, 2003)

Hi there, well this has me completely stumped. both my filters (Eheim cannisters 2026 pro2) after lights on until lights off are producing little bubbles in bursts at 10-15minutes.

At first I thought that I had a leak in the sytem. So I went to the expense of replacing all the seals, checked for alignment of the baskets, one of which is not real good.

Then the same thing kept happening.

So this morning I waited for the lights to come one and watched. For about 1 1/2 hours nothing, no bubbles. Then slowly bubbles started. By about 3 hours after lights on the same thing was full on. Burst of bubbles every ten to fifteen minutes.

I think it might be plants pearling close to the intake. I currently have 2.8 watts per gallon, Dupla CO2 sytem (co2 at 22ppm), and heavily planted.

Am I right, has anyone else seen this, and what can I do?

Rumple

Beware of the hand that feeds you!!


----------



## Rex Grigg (Jan 22, 2004)

I have seen it. If you have eliminated any chance of air leaks in your filtration system then what is happening is water is saturated with gas, either CO2, or O2 or a combination. When the water goes though the filter the gas separates from the water. And after a while the filter purges it.

Moderator










American by birth, Marine by the grace of God! This post spell checked with IESpell available at http://www.iespell.com

See my Profile for tank details.


----------



## Rumpled (Jun 23, 2003)

I think I have limited the effect of this annoying problem.However, this has come at a price, I reduced the flow on the 2026 which is doing it the most, not a lot but enough so that the bubbles only happen every half an hour. This give the other smaller bubbles time to dissipate in the water column. Much nicer looking and less like a bubble bath.

I agree with you, Rex, this is the only possible cause of the bubble problem as I have gone to the extent of searching the entire hoses to see if there is a puncture in the line, as well as the aforementioned replacement of seals.

Anyway if anyone can come up with a solution I am more than happy to listen.

Rumple

Beware of the hand that feeds you!!


----------



## gpodio (Feb 4, 2004)

What is most likely happening is that the pump is creating a weak vacum in the canister and drawing O2 and/or CO2 out of the water (or other gases). In my canisters this is an indication that my media is starting to clog and posing too much of a resistance to the pump. If the pump was at the bottom of the filter you would not have this effect. You can either clean or re-arrange your filter media or change it for a different type so that there is less resistance made to the water flow, at times too much media can have this effect, so can media that is too fine such as micron pads or too much filter floss. A dirty pre-filter or restricted intake tube also has the same effect. You can turn the pump down to reduce the vacum and that will help as you have already done but may not solve the problem. This is why the intake tube is larger than the output tube. A good example of this effect is to suck up some tank water into a syringe, block the end and create a vacum by pulling the plunger out, you'll see the water bubbling as the gas is 'sucked' out by the negative pressure.

Hope that helps, you should have no problem eliminating this completely if you eliminate any resistance prior to the pump.

Giancarlo Podio


----------



## Justin Fournier (Jan 27, 2004)

I have lots of issues revolving around disolved gasses comming out of solution in my filter. 

I just stopped playing with it and removed the micro filtration pads, everything has been fine since. Once a week or so I give the canister a goooood shake to make sure all the air is out of it. Other then that I have not found any good solutions.


----------



## gpodio (Feb 4, 2004)

That IS a good solution!









Any time I use micron pads before the pump I have the same thing happen. If possible, find a way to add the pads after the pump, difficult in most canisters however you could try using something inline in the filter output tube if the pump can handle it.

Giancarlo Podio


----------



## Justin Fournier (Jan 27, 2004)

It's only a good solution if you don;t need the micro filtration







Otherwise your tank might be cloudy!


----------



## gpodio (Feb 4, 2004)

Why is your tank cloudy? I've never found the need to filter with micron pads 24/7, I only really use them after a tank has been setup or the substrate severely disturbed. Even then it only takes a couple of days to clear up on it's own. What I do now is keep a Duetto dj-100 full of carbon chips and layers of micron pads cut to size in between the carbon, it's ready to go any time I need it and I don't have to touch the canister to use it on the rare occasions it's needed. Perhaps this could be an alternative. Filter floss is about as fine as I use in the canister now, it filters small particles but lets a lot of water through until it clogs up, not quite as fine as micron pads but again, you shouldn't need to use micron pads all the time,if so you should be looking into the cause of the cloudyness.

Hope that helps
Giancarlo Podio


----------



## gsmollin (Feb 3, 2003)

The previous responses have been pretty accurate, but I would like to add a small comment.

Regardless of where the pump is located it can cause outgassing of the water. Centrifugal pumps cause a partial vacuum at the impeller even when they are not restricted by clogged media, or micron filters. Just the water path can contribute to the problem: The water is under increasing pressure as it travel down the inlet tube to the cannister, and gas in the water can dissolve. As it travels back up the tube and exits the return, the pressure is released, and gas can evolve. A clogged filtering medium can exaserbate this problem of course- it can cause outright pump cavitation- but the basic effects are always present.

In a planted aquarium the plants evolve O2, and it dissolves into the water until saturation level is reached, and then pearling can begin. Most plant-loving aquarists aspire to this condition. Well, when the plants are pearling, the slightest disturbance to the water will cause O2 to evolve, so you can expect your filter to have bubbles in the return as a natural consequence.

My Magnum 350 has a powerful pump, and bubbles are seen in the return line pretty much all the time when the lights are on. At night, I don't notice it, but I haven't really been interested enough to search for them. I would expect the Eheim to bubble a lot less than the Magnum, since its pump is weaker, and derated so much.

So this brings me to my question about this thread: Why do you care if a few bubbles are in the return water, now that you know it's not a leak?


----------



## gpodio (Feb 4, 2004)

First of all I never see bubbles in my canisters (Eheim) unless the media or pre-filter is clogging, even towards the end of the day when pearling is at it's greatest. I think the small vacum created at the impeller is not the same as the entire volume of the canister being subject to the vacum. If the canister is brough up to tank level then yes, the vacum at the impeller will be greater because the pump is sucking water into the filter instead of just pushing water back into the tank. Positioned under the tank there is sufficient water pressure from the oversized intake tube to compensate for any vacum created at the impeller, at least with these filters the intake carries more volume than the output tube, making it quite difficult to create a vacum inside the canister itself.

The reasons why some would want to avoid this can be; loss of CO2, potential cavitation and air locking of the pump, loss of oxygen and therefore reduced pearling, noisy pump operation and increased wear on the impeller assembly.

If you only see a little bubbling from your filter towards the end of the day then it's no big deal, but it can be worse than that in some cases where media that is either clogged or too restrictive is at fault.

Giancarlo Podio


----------



## Justin Fournier (Jan 27, 2004)

I don't use any fine filter media, and when I stir the substrate, the tank is only cloudy for a day.

But I am not everyone, people using laterite under gravel may require water polishing more frequently.

If it was not for the nutrients I add to my tank, I would prefer to drink that water over my tap water


----------



## gpodio (Feb 4, 2004)

Who knows, even with all those nutrients it may still be better than tap water


----------



## gsmollin (Feb 3, 2003)

The bubbles are O2. CO2 is way too hydroscopic to come out of solution that easily. Do you ever hear the pump cavitate? Even though my Magnum spits bubbles I never hear them go through the pump. If the water is not at O2 saturation, the bubbles won't be seen, so I think it's got little effect on pearling.


----------



## Justin Fournier (Jan 27, 2004)

Could very well be O2. My tanks usually has 10-15 streams of bubbles heading to the top of the tank, and all the plants underleaves are covered with bubbles. I am sure my tank is saturated.


----------



## Rumpled (Jun 23, 2003)

GSmollin, in response to your question about why I care about a few bubble, it is simply this. It is not just a few bubbles, it is an absolute torrent, the whole tank looks like a bubble bath gone mad. My plants are pearling which is fantastic, however the whole picture is being ruined by twenty thousand fine bubbles moving through the tank. Not really what I would call a few bubbles. If I had a video camera I would show you what I mean.

Anyway thanks all for your comment. I have found that I lift the output lever a little this tends to help reduce the flow of bubbles.

Rumple.

Beware of the hand that feeds you!!


----------



## Rumpled (Jun 23, 2003)

Incidently, my filters were only cleanedtwo weeks ago and even then it was not clogged. The pumps do not cavitate.

I am not worried about the loss of CO2, I just wanted to know how to reduce this since I have already gone to the trouble of replacing seals.

Beware of the hand that feeds you!!


----------



## gsmollin (Feb 3, 2003)

> quote:
> 
> Originally posted by Rumpled:
> Hi there, well this has me completely stumped. both my filters (Eheim cannisters 2026 pro2) after lights on until lights off are producing little bubbles in bursts at 10-15minutes...
> ...


I may have missed something here, but that description gave me the impression it was just a few bubbles, every 10 or 15 minutes. I've never seen a torrent of bubbles come out of the outlet, even when the tank was pearling, pretty well full-tilt. I'm not sure how you're getting that much gas into the water either. Perhaps you could try lowering the inlet to the gravel level, where there should be the least amount of tiny bubbles. Otherwise the recommendations to keep media clean, clean you hoses, and pump, and otherwise lower back-pressure on the pump may help.


----------



## Justin Fournier (Jan 27, 2004)

I have the occasional turrent of micro bubles comming from the filter, and this only really started to happen when I switched my intake on the Eheim to the surface skimmer. 

What type of intake system do you have Rumpled?


----------



## Rumpled (Jun 23, 2003)

Both inlets are the standard Eheim inlet. Down near the gravel line.

Beware of the hand that feeds you!!


----------



## Justin Fournier (Jan 27, 2004)

How much pearling do you have?


----------



## Rumpled (Jun 23, 2003)

50% of plants pearl everyday for around 5 hours.

Beware of the hand that feeds you!!


----------



## Justin Fournier (Jan 27, 2004)

Your water is probably saturated with 02 then.. Try messing with your media as previous posts have explained. Other then that you might have to change the setup to accomodate this.


----------



## gpodio (Feb 4, 2004)

Try restricting the output tube, either with a spray bar (under water) or just obstruct the tube a little. This should help if infact the filter pressure is at fault. I think you will see some improvement.

Hope that helps
Giancarlo Podio


----------



## gsmollin (Feb 3, 2003)

GP may have a good idea. Restricting the outlet will raise back-pressure on the pump, and reduce the partial vacuum at the pump inlet. This has to be approached carefully though; some pumps stall abruptly when the back-pressure exceeds their limit.


----------



## Justin Fournier (Jan 27, 2004)

Eheims and Renas both can handle some back pressure. I would not worry exerting a small amount of back pressure on them to reduce the vacum inside the canister.


----------



## Jon Mulzer (Mar 9, 2003)

Back pressure will not hurt a centrifugal pump. In fact it lessens the current draw because it has less water to accelerate against the outer wall of the impeller housing. The only possible thing there is to worry about is if you completely constricted the flow in a centrifugal pump that was cooled by what it is pumping. You would not have to worry about this in your case.

Piston and diaphragm pumps are the only types I can think of that stall with excess back pressure.

----------------------------

15XH, 36W PC, XP-1, Onyx Sand, DIY CO2

Crypts spiralis, ciliata and wendtii bronze and red, pennywort, wisteria and java fern and moss.


----------



## Rumpled (Jun 23, 2003)

Well, I have reduced the flow of my filters and this has helped a bit, and it is not as violent as before.

I want to thank all those who contributed to this thread. It seems that my suspicions were correct and that I have a turbo charged tank full of O2.

If anyone has anymore to contribute by all means do as I have read with great interest to the replies.

Thanks

Rumples

Beware of the hand that feeds you!!


----------



## gsmollin (Feb 3, 2003)

Yes, you can stall a centrifugal pump, as well as an axial-flow. The definition of the word "stall" is not related to the spinning of the impeller, but rather the flow-rate v.s. head pressure curve. In some pumps, the flow rate is fairly flat with head pressure until a critical pressure is reached, then the flow rate rapidly decreases; the "stall region" of the pump has been reached. In other pumps, the flow rate v.s. head pressure is a drooping curve, and doubling the head pressure roughly halves the flow rate.

Piston and diaphragm pumps are the logical result of flattening the flow rate graph. When they stall, it is very abrupt, and can result in the piston stopping as well.

I expect an Eheim pump falls into the "drooping" category, because the pump is so large compared to its pumping capacity. However, that's only a guess, since I haven't tried it and I don't have data from Eheim.


----------



## gpodio (Feb 4, 2004)

Keep in mind that most Eheims are either shipped with spraybar or one is available separately so my guess is that they are designed with a little head pressure in mind. Personally I can't see this kind of pump stalling due to restricted flow as long as the height does not exceed the rated value. Even with a tiny hole left in the output tube the pump will continue to turn, continue to create pressure in the tube and so water will continue to come out of the little hole. That doesn't sound like stalling to me. If anything, you might not have sufficient water movement to cool the pump down but you won't want to restrict the flow that much. The most restricted canister I have at the moment is an Eheim 2217 with a spray bar which has been cut down to only 3 holes where water comes out from. It's on it's 2nd year now and no problems yet.

Hope that helps
Giancarlo Podio


----------



## Jon Mulzer (Mar 9, 2003)

I didn't think of stalling in that context. When I think of stalling, I think of *screech* *clunk* *smoke* type of stalling.







Which is why I referenced piston and diaphragm pumps.

----------------------------

15XH, 36W PC, XP-1, Onyx Sand, DIY CO2

Crypts spiralis, ciliata and wendtii bronze and red, pennywort, wisteria and java fern and moss.


----------

