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Spray bar mod/surface agitation help

aec34

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10 Oct 2020
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Gloucestershire
My Dennerle scaper tank 35l is doing pretty well, but I have no surface agitation and am starting to get a bit more scum.
I don’t run CO2 and the problem is mostly aesthetic, but I’d like to try to slightly alter my filter - help!

I currently have an Aquael pat mini in the back right corner, with the duck bill pointed against the back wall. Photo from above, and from front (pre water change):
3D0976DF-E2AD-4D46-8B55-4F48A173A165.jpeg

584BD319-706F-48A7-BD38-79C13E1FD2A7.jpeg

I tried angling it up, but then had to turn the filter up too much to get any agitation. I don’t want to change the filter - I like the fact it’s internal, the sponge is dead easy to clean and it’s quiet. Any suggestions? Space is also quite tight. I don’t mind some light DIY, but pumps etc. are a bit of a mystery so I’ll need guiding through this.
 

AlecF

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15 Sep 2021
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Unhelpful of me, as I'm no technician, and I get the need for flow and agitation, but I'm always interested when we call it bodily (good) and when it's scum (bad). It's one of the paradoxes of the hobby, like mulm, where I'm always aspiring to healthy decay and at the same time worried about dirty substrate. Anyway, I hope someone can say something more helpful, but I'd love to know if that scum is a bad thing or not?
 

tam

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5 May 2011
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1,294
Use the venturi on the pat mini now and then and the air will break up the surface - you don't need it all the time, so just run it when your not there and you'll probably find that's enough to keep the film away when you are :)
 

aec34

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Use the venturi on the pat mini now and then and the air will break up the surface - you don't need it all the time, so just run it when your not there and you'll probably find that's enough to keep the film away when you are :)
Ok, so I found out last week by accident what a Venturi is - I feel a right numpty asking this, but how do you attach it? I’m not entirely convinced I’ve got my set up as Aquael intended. At the moment I have a tube which Im using as the air inlet coming off the pokey out bit by where the duckbill is. Do I need to cut a short bit of tubing to go between the Venturi and the adapter (to go between duckbill and pokey out bit)? Well done if anyone understands this description....
 

aec34

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Unhelpful of me, as I'm no technician, and I get the need for flow and agitation, but I'm always interested when we call it bodily (good) and when it's scum (bad). It's one of the paradoxes of the hobby, like mulm, where I'm always aspiring to healthy decay and at the same time worried about dirty substrate. Anyway, I hope someone can say something more helpful, but I'd love to know if that scum is a bad thing or not?
Indeed - my shrimp tank basically has a forest floor. I really don’t think the scum/film is doing any harm, it just looks, well, scummy...
 

Garuf

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Is it the stock dennerle? If so given that the scapers flow outlet fits onto standard 12/3mm tubes I suspect the aquaneo skimmer might fit onto it.
 

aec34

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Is there an airline tube going out from the pokey out bit out above the waters surface?

Or to to be clear, the pokey out bit needs a tuby wuby above the splashy washy and.. heck heres a picture

View attachment 177106
Ok, so far so good! The tuby wuby is indeed above the splashy washy.

Edit: think I might not have the flow high enough to make much difference. Will experiment
 
Last edited:

Hufsa

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@aec34 are you getting airbubbles coming out the the outlet/duckbill? If not you might have to blow some air through the tube to get it started, then it will keep going on its own. Im not sure I would call it agitation, but every bubble has a surface area between the air inside and water, so when you are adding airbubbles to a tank you are essentially giving yourself a bigger gas exchange surface/area of your tank, if that makes sense. That is why smaller bubbles are better than bigger bubbles, because small bubbles have a better surface to air ratio. I suppose the bubbles also create a bit of surface agitation when they reach the top of the water and burst.
 

Hufsa

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Edit: think I might not have the flow high enough to make much difference. Will experiment
Ah, that might be it then. You need a certain amount of flow through the outlet of the filter, in order to "pull" in air through the tube. If you have a dinglybop on the end of the tube, make sure this is open fully, or even try to remove the dinglybop to allow the air free passage into the tube. Unlike the picture I showed, I would affix the end of the tube somewhere -above- the surface of the water, just in case something goes wrong, you dont end up with water dripping out of your tank through a siphon
 

aec34

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Thanks so much @Hufsa - got it working now 🙂 Turns out I needed to turn the flow up, and then twiddling the dinglybop makes a difference to bubbles.
Good tip @tam on only using it on when it won’t be annoying to be in the same room as it.
 

tam

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Glad you figured it out. I just run it now and then when I want to clear the film or when it gets very hot in summer as I don't like the noise either. Great filters though - small, flexible, easy to clean and do the job well.
 
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