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Oase bio master 850 noisy air problems

Joanne.S

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25 Mar 2022
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Hey guys any help would be appreciate. My Oase 850 gets trapped air, there is gurgling in the pump then a whoosh of air going into the tank.
any ideas how I can stop his.
I have a 450lt discus tank with one 350 bio master and one 850 bio master. it’s driving me nuts
 
Solution
It's quite common for canister filters, generally caused by small amount of air being sucked in on the inlet side of the pump, using through pipe connections. The amount of air is generally too small to detect and it can happen even when the pipe work looks like it is well connected. It can also happen it an air-stone is too close to the inlet and bubbles are entering that way.

The easiest way to think about it is that the pump is sucking water through the inlet pipe and blowing it through the outlet pipe. The sucking can draw in air through pipe connections, and the strength of the sucking force is also dependent on how much water can flow tough the pipe. This a bit of a simplification of the physics, but I hope you get the idea...
It's quite common for canister filters, generally caused by small amount of air being sucked in on the inlet side of the pump, using through pipe connections. The amount of air is generally too small to detect and it can happen even when the pipe work looks like it is well connected. It can also happen it an air-stone is too close to the inlet and bubbles are entering that way.

The easiest way to think about it is that the pump is sucking water through the inlet pipe and blowing it through the outlet pipe. The sucking can draw in air through pipe connections, and the strength of the sucking force is also dependent on how much water can flow tough the pipe. This a bit of a simplification of the physics, but I hope you get the idea.

The solutions are:
1. Put hose clips onto all connection on the inlet side.
2. Make sure any flow regulators on the inlet side are fully open. Only control the flow on the outlet side.
 
Solution
Thank you for your advice, I will check all the connections and piping, continue to tilt and see how it goes.
I will keep you updated 😊
 
I have an Oase 850 Thermo and a 600 Thermo.
They start sucking air when the pre-filters need cleaning or when the fish knock an air stone into the path of the inlet which is always worth a check.
 
I’ve run six different canisters over the years and never had one of them suck in air, including my 350 Biomaster.
After cleaning I’ve always rocked canister filters gently to expel the inevitable trapped air. The Biomaster though seems very good at getting rid of the air so doesn’t seem to need much rocking. Maybe I’ve just been lucky.
 
I’ve run six different canisters over the years and never had one of them suck in air, including my 350 Biomaster.
After cleaning I’ve always rocked canister filters gently to expel the inevitable trapped air. The Biomaster though seems very good at getting rid of the air so doesn’t seem to need much rocking. Maybe I’ve just been lucky.
Maybe you just clean yours more than me :) It's not trapped air. It seems to suck air in from somewhere when it's blocking.
 
Hey guys any help would be appreciate. My Oase 850 gets trapped air, there is gurgling in the pump then a whoosh of air going into the tank.
any ideas how I can stop his.
I have a 450lt discus tank with one 350 bio master and one 850 bio master. it’s driving me nuts
Hi Joanne,
I have few questions: can you let us know when whooshing is happening during the day? Do you have plants and how many? Are you having co2? Glass lily pie with skimmer on the suction pipe? How long are you hoses and do you have any additional on line gear?
Maybe, you post some pictures of your filter system form the entry to the exit.
Regards
 
It's quite common for canister filters, generally caused by small amount of air being sucked in on the inlet side of the pump, using through pipe connections. The amount of air is generally too small to detect and it can happen even when the pipe work looks like it is well connected. It can also happen it an air-stone is too close to the inlet and bubbles are entering that way.

The easiest way to think about it is that the pump is sucking water through the inlet pipe and blowing it through the outlet pipe. The sucking can draw in air through pipe connections, and the strength of the sucking force is also dependent on how much water can flow tough the pipe. This a bit of a simplification of the physics, but I hope you get the idea.

The solutions are:
1. Put hose clips onto all connection on the inlet side.
2. Make sure any flow regulators on the inlet side are fully open. Only control the flow on the outlet side.
Yes, it definitely could be all of those things or possibly just because he's running an Oase.

Many, many people have this issue with Oase and not with several other canister filter brands/models from my research. Personally, I think Oase has a design flaw(maybe too many seals in the design or just poorly designed ones that are prone to leaking air if not seated absolutely perfectly) that even seams worse on the Thermo models. All you have to do is look around as there are whole threads on the issue. I don't see many threads about this if any with some other brands.

I was going to buy a Oase Biomaster Thermo but, all of the issues I read about caused me to go another way. I have no personal experience but, I just thought I would point this out in case the OP wasn't aware.
 
My Oase Biomaster 600 was continually collecting, and periodically purging, air. I could rock the canister filter back and forth for 3-4 mins to completely empty it of trapped air, then return 30 mins later to find yet more air had become trapped inside ! When rocking the filter to dislodge the trapped air, the impeller would even temporarily stall such was the volume of trapped air. For ages this problem was really concerning and frustrating me as I couldn't understand what was causing the trapped air, and I didn't like the fact a new and expensive filter was seemingly leaking air around a connection and potentially wasn't fully watertight. At the time, I was running an air stone on the aquarium so the water was always super aerated. The air stone was at least 12 inches away from the filter intake so I naturally didn't ever think it could be the source of the filter taking on too much air. My aquarium is in my bedroom and over time my air pump became noisier than I was happy with, so I did away with it. To ensure the tank maintained a decent level of aeration I simply turned the Biomaster outlet upwards to increase surface agitation ........I also have a heavily planted tank which helps. After removing the air pump, the problem with the filter taking on air immediately resolved. I've tried to rock the filter, to check for trapped air, on numerous occasions since removing the air pump and there has never been any air trapped. I've therefore concluded that having an efficient air stone on the tank, providing highly aerated water with all the little visible micro-bubbles, is what was causing my Biomaster to continuously fill with air it needed to purge. For me, its problem solved and a relief to realise the trapped air was coming from within the aquarium and apparently not bypassing an external seal or connector.
 
I’ve had my Biomaster 350 for a while now and have found it’s so much better than any other canister I’ve had at expelling trapped air after routine maintenance that I don’t need to rock it anymore. The priming pump is also the best I’ve used to date.
 
My Oase Biomaster 600 was continually collecting, and periodically purging, air. I could rock the canister filter back and forth for 3-4 mins to completely empty it of trapped air, then return 30 mins later to find yet more air had become trapped inside ! When rocking the filter to dislodge the trapped air, the impeller would even temporarily stall such was the volume of trapped air. For ages this problem was really concerning and frustrating me as I couldn't understand what was causing the trapped air, and I didn't like the fact a new and expensive filter was seemingly leaking air around a connection and potentially wasn't fully watertight. At the time, I was running an air stone on the aquarium so the water was always super aerated. The air stone was at least 12 inches away from the filter intake so I naturally didn't ever think it could be the source of the filter taking on too much air. My aquarium is in my bedroom and over time my air pump became noisier than I was happy with, so I did away with it. To ensure the tank maintained a decent level of aeration I simply turned the Biomaster outlet upwards to increase surface agitation ........I also have a heavily planted tank which helps. After removing the air pump, the problem with the filter taking on air immediately resolved. I've tried to rock the filter, to check for trapped air, on numerous occasions since removing the air pump and there has never been any air trapped. I've therefore concluded that having an efficient air stone on the tank, providing highly aerated water with all the little visible micro-bubbles, is what was causing my Biomaster to continuously fill with air it needed to purge. For me, its problem solved and a relief to realise the trapped air was coming from within the aquarium and apparently not bypassing an external seal or connector.
Thanks for the input and I'm glad you got your issue sorted👍. Others have had similar issues/theories with CO2 injection as well.

I don't think your experience accounts for all of the air purging reports with Oase though(there is a very large volume all over the net). I have one of the finest bubble air stones I have ever seen(Aquario Neo Diffuser Air) in my UNS 60U about 9 inches from the intake of my Fluval 207. It is so fine that I can see microbubbles dispersed all the way on the other side of the tank. But, I still have zero air accumulation or air purging issues with the Fluval. Now, would I with an Oase Biomaster? I can't say for sure but I can say that the more O-ring sealed passages and complication in general, the more chance of air/water leakage or failure. And, the Oase is one of the most complicated designs on the market(especially the Thermo models)with many O-ring sealed passages and potential failure points.

So, for me anyway, Oase wasn't worth the risk. Especially when Fluval and Eheim, just for instance can usually be found for a lower price(over here anyway) and with Fluval you get an extra year of warranty over Oase. Both are simple designs with less passages for air to get in too. And, the Fluval is pretty easy to clean too with its aquastop/prefilter design.

That said, I would still like to try an Oase Canister one day. I have there new CrystalSkim 350 and it is a very nice little Skimmer(maybe the nicest one on the market). I almost went with a FiltoSmart for my new 27L Nano Cube build but, went with an Eheim Classic instead as it was cheaper on sale and is a better design imo that allows for more/easier media customization.

Edit: More clear and concise.
 
Last edited:
Thanks for the input and I'm glad you got your issue sorted👍. Others have had similar issues/theories with CO2 injection as well.

I don't think your experience accounts for all of the air purging reports with Oase though(there is a very large volume all over the net). I have one of the finest bubble air stones I have ever seen(Aquario Neo Diffuser Air) in my UNS 60U about 9 inches from the intake of my Fluval 207. It is so fine that I can see microbubbles dispersed all the way on the other side of the tank. But, I still have zero air accumulation or air purging issues with the Fluval. Now, would I with an Oase Biomaster? I can't say for sure but I can say that the more O-ring sealed passages and complication in general, the more chance of air/water leakage or failure. And, the Oase is one of the most complicated designs on the market(especially the Thermo models)with many O-ring sealed passages and potential failure points.

So, for me anyway, Oase wasn't worth the risk. Especially when Fluval and Eheim, just for instance can usually be found for a lower price(over here anyway) and with Fluval you get an extra year of warranty over Oase. Both are simple designs with less passages for air to get in too. And, the Fluval is pretty easy to clean too with its aquastop/prefilter design.

That said, I would still like to try an Oase Canister one day. I have there new CrystalSkim 350 and it is a very nice little Skimmer(maybe the nicest one on the market). I almost went with a FiltoSmart for my new 27L Nano Cube build but, went with an Eheim Classic instead as it was cheaper on sale and is a better design imo that allows for more/easier media customization.

Edit: More clear and concise.
Sure, I would agree that my experience is unlikely to be the solution to everyone who's experiencing the air accumulation and purging with their Biomaster filters. I mean, like you say, the internet has many accounts of people with this problem and I certainly wouldn't expect all those people to be running air stones on their tanks. I wanted to share my experience of resolving the annoying & concerning air purging issue with this filter in case it worked for anyone else afflicted with the issue. When initially researching the issue online, I would regularly see all manner of labour intensive recommendations being made to resolve the issue. Recommendations such as, 'apply silicone gel to every gasket and o-ring' (many of which are tricky to access), 'dismantle all tubing and thoroughly clean it', 'shorten all tubing to the minimum length possible', .......etc, etc. Unsurprisingly, these suggestions generally didn't make any difference to the problem whatsoever. Once I'd, inadvertently, stumbled upon a much simpler and immediate solution to the issue, in my case at least, I thought it'd be worthwhile to share it and potentially save some other people from trying more frustrating attempts at a fix.

I can totally relate to your situation of having an efficient air diffuser emitting copious amounts of fine micro-bubbles, yet experiencing no air purging issues with your Fluval canister. Over the years, I've run similar air diffusers on tanks with various Fluval and Eheim canister filters and I've never before experienced the air purging issues I experienced with the Oase Biomaster. My theory is that maybe its something about the internal pump head design/configuration with the Biomaster that renders it prone to accumulating air, from heavily aerated tank water, and periodically purging it in noticeable bursts once its reached a relatively large amount. Whereas perhaps the other filters are better at continually ejecting any air in a consistent and much less obvious manner due to their differing internal pump head design.

I would agree with you that the number of o-rings/gaskets that the Biomaster possesses, in relation to other external canister filters, is definitely likely to increase the chances for air ingress (or water loss) into the system. However, in my case, none of these appeared to the cause of the problem. As previously mentioned, I've owned various Fluval & Eheim external filters before, and now I've resolved the air purging issue with my Oase Biomaster, I can confidently say that its the best and easiest (in terms of performance & maintenance) filter I've ever owned ---- I've had it for 2 years now. I clean the prefilter every fortnight (5 min job) and the main filter every 6 months. I've only used Oase, Eheim & Fluval externals and my second most preferred filter type would be Eheim, followed by Fluval ........Fluval in last place because I had one spontaneously leak and flood/ruin a floor. I too am a fan of the old Eheim Classic filters and had one in reliable operation for over 15 years !
 
Sure, I would agree that my experience is unlikely to be the solution to everyone who's experiencing the air accumulation and purging with their Biomaster filters. I mean, like you say, the internet has many accounts of people with this problem and I certainly wouldn't expect all those people to be running air stones on their tanks. I wanted to share my experience of resolving the annoying & concerning air purging issue with this filter in case it worked for anyone else afflicted with the issue. When initially researching the issue online, I would regularly see all manner of labour intensive recommendations being made to resolve the issue. Recommendations such as, 'apply silicone gel to every gasket and o-ring' (many of which are tricky to access), 'dismantle all tubing and thoroughly clean it', 'shorten all tubing to the minimum length possible', .......etc, etc. Unsurprisingly, these suggestions generally didn't make any difference to the problem whatsoever. Once I'd, inadvertently, stumbled upon a much simpler and immediate solution to the issue, in my case at least, I thought it'd be worthwhile to share it and potentially save some other people from trying more frustrating attempts at a fix.
Yes, definitely a good thing you posted your solution👍. Hopefully it helps at least a few people.
I can totally relate to your situation of having an efficient air diffuser emitting copious amounts of fine micro-bubbles, yet experiencing no air purging issues with your Fluval canister. Over the years, I've run similar air diffusers on tanks with various Fluval and Eheim canister filters and I've never before experienced the air purging issues I experienced with the Oase Biomaster. My theory is that maybe its something about the internal pump head design/configuration with the Biomaster that renders it prone to accumulating air, from heavily aerated tank water, and periodically purging it in noticeable bursts once its reached a relatively large amount. Whereas perhaps the other filters are better at continually ejecting any air in a consistent and much less obvious manner due to their differing internal pump head design.
Yes, I have considered this as well and think it is a valid hypothesis. The key conclusion though imo is that the Biomaster is a flawed design that needs improvement. It shows problems where others don't and these problems are widespread.
I would agree with you that the number of o-rings/gaskets that the Biomaster possesses, in relation to other external canister filters, is definitely likely to increase the chances for air ingress (or water loss) into the system. However, in my case, none of these appeared to the cause of the problem. As previously mentioned, I've owned various Fluval & Eheim external filters before, and now I've resolved the air purging issue with my Oase Biomaster, I can confidently say that its the best and easiest (in terms of performance & maintenance) filter I've ever owned ---- I've had it for 2 years now. I clean the prefilter every fortnight (5 min job) and the main filter every 6 months. I've only used Oase, Eheim & Fluval externals and my second most preferred filter type would be Eheim, followed by Fluval ........Fluval in last place because I had one spontaneously leak and flood/ruin a floor. I too am a fan of the old Eheim Classic filters and had one in reliable operation for over 15 years !
Well for me personally, the air purging issues, higher price point, shorter warranty, reports of higher noise output comparatively(a lot of variation is reported too), and weird Filtration pathway eliminate the Biomaster from the running. The pre-filter is just not enough of a benefit imo to put up with all of the other issues. Especially when Fluval offers a prefilter design that is only slightly more trouble/time consuming to clean. Their 07 Series is my personal favorite so far of the Canisters I have tried/tested. Of the ones I haven't tested, the ADA/Fzone stainless steel canisters are the best on the market imo with the most reliable and easily serviceable design. They don't offer the ease of maintenance that some pre-filter equipped models do but make up for it in many other ways... Aside from a new pump now and then, they are lifetime purchases.

All of that said, I still understand why others choose to try/run Oase Biomaster. That pre-filter design is nice and is the easiest to maintain on the market that I know of. They also seam pretty reliable and liked other then the issues I outlined. I have almost tried them myself a number of times. In fact, there was a good sale just on on a Biomaster 250 but, after reading the reviews(they were riddled with more reports of purging issues) I went with an Eheim Classic instead(it was also half the price). At the end of the day, I just want a filter that runs quietly(as clese to silent as possible) for years on end without me having to ever worry about it or deal with any problems. I'm fine with a little more maintenance as long as I get those qualities along with crystal clear water and a high turnover rate...
 
I can't say for sure but I can say that the more O-ring sealed passages and complication in general, the more chance of air/water leakage or failure. And, the Oase is one of the most complicated designs on the market(especially the Thermo models)with many O-ring sealed passages and potential failure points.
There are a few more seals in my Biomaster 350 than my other canister filters but these are inside the filter itself so I don’t see how air could get in this way. As far as I’m aware the Thermo 350 doesn’t have any more O rings than my non thermo model? There is an O ringed sealed cap where the heater goes. Perhaps I’m wrong but I thought you just took the cap off and installed the heater with its own O ring?
I bought spare seals for mine, the main gasket and pre filter gasket. I need to get the two for the inlet/outlet connection unit. Apart from any other hose connections that any filter will require I can’t see where air can get sucked in unless it’s going directly into the main inlet pipe (operator error) ?

Thinking about this further my Tetratec and Sera canister filters both have the same number of potential places to leak water or suck in air as the Biomaster. I had a water leak on the inlet manifold of my Tetratec a while back that required a whole new unit. The simplest is my Eheim Classic and that only has the main gasket, an O ring inside the head unit and one on the inlet pipe.
 
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