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Can't get my flow right - weird pattern

Aetherial

Member
Joined
17 Feb 2021
Messages
32
Location
The Netherlands
Hey all,

I've been trying to get a nice circular flow pattern for the past few weeks, but I just can't seem to figure it out.
Everything I've tried so far leads to "chaos" with the flow randomly going in all kinds of directions.
I'm using an Oase Biomaster Thermo 350 on a 100L tank, with the standard inlet and spray bar that came with the filter.

I've tried:
The full length spray bar (2 shorter bars with a piece of tubing connecting them) along the back, holes pointing straight forward, holes angled slightly upwards, holes pointing more upwards than forward, spray bar right below surface, farther from surface, etc.
Only 1 half of the spray bar, centered along the back, angles, etc., mentioned above.
1 half of the spray bar on the left side, pointing across the length of the tank, but that didn't fit as the spray bar was just a little too long.
The "Flow Distributor" that came with the filter, which is kind of a very small lily pipe.
Nothing attached to the outlet.

In the end, I've gone back to the full length spray bar along the back, holes angled slightly upwards, as I felt like that gave the best result.
However, that hasn't solved the problem at all.

Here's a video of what the flow currently looks like. You can clearly see the different directions of the flow when looking at the co2 bubbles on the surface. About halfway into the video, you can also see a loose leaf going back and forth in the flow.
Side note: I forgot to remove the audio before uploading the video, so unless you'd enjoy hearing me sigh and moan like an old man when moving around, I'd recommend muting it 😂




My DC is lime green wherever I place it, and I get a pH drop of around 1.2, so I'm not too concerned about co2 distribution, but I'd assume this chaotic flow pattern might/will/does create problems.
Also, the highest part of the wood is actually below the spray bar, even though it looks like it's at the same height in the video, so it's not blocking the flow directly.

One more thing I thought might be worth mentioning, just in case, is that the water comes out of the spray bar holes at an angle, rather than straight forward.
Made a little drawing, so I hope it makes sense:
spraybar.jpg
 

Zeus.

Fertz Calc Meister
Joined
1 Oct 2016
Messages
3,925
Location
Yorkshire,UK
Plants are looking good :thumbup:

The flow isnt bad, but not great, filter output is x10, but what media have you got in your filter- if full of filter floss and packed with ceramic media - I would remove the filter floss half the ceramic and the fine sponges, a planted tank has plants and they will take care of the Biological filtration, this will increase filter output and flow through filter at the same time. Better flow in filter gives better O2 levels in filter and aid the breakdown of nitrogen compounds as well.

Once filter is optimised as above and if flow in the tank not improved, next on list is number of holes in spraybar and size, less holes and/or smaller hoes will create more of a jet action, the jet action is due to the water leaving the holes at a higher velocity and will have more energy, this higher energy will create more flow in tank, yes the output from filter will be less, but will create more flow/turnover and flow is king. You could try taping up half the holes to start with.

When tank is half full of water at WC and filter is on how far does the water go from the spraybar?, ideally it should reach the front.

Ideally the CO2 bubbles should be jetted to the front of the tank and right down to the substrate level.

Getting the flow right at first will pay off later esp when the plants fill, as they will reduce the flow and thats when the plants may suffer
 

ceg4048

Expert/Global Moderator
UKAPS Team
Joined
11 Jul 2007
Messages
9,323
Location
Chicago, USA
I agree with Karl. The next step is to remove about 2/3rds of the filter media, especially the silly rings or hoops, which are specifically designed to slow the flow so that large debris can settle out and get trapped.

Cheers,
 

Aetherial

Member
Thread starter
Joined
17 Feb 2021
Messages
32
Location
The Netherlands
Plants are looking good :thumbup:
Cheers! A couple days ago I trimmed all the stem plants down to the first node above the substrate, and then cut up and replanted the rest to try and get it all nice and bushy, hence the relatively low height at the moment.
I've got some BBA and Staghorn here and there, but overall, the plants are doing quite well! I've definitely noticed an improvement since switching from AIO to EI. The Alternanthera did go from deep red to a lighter red and even some green here and there, which I suspect is due to the higher amount of NO3 in my EI mix, compared to the AIO, but no big deal.

The flow isnt bad, but not great, filter output is x10, but what media have you got in your filter- if full of filter floss and packed with ceramic media - I would remove the filter floss half the ceramic and the fine sponges, a planted tank has plants and they will take care of the Biological filtration, this will increase filter output and flow through filter at the same time. Better flow in filter gives better O2 levels in filter and aid the breakdown of nitrogen compounds as well.
Currently, the filter media is:
Bottom tray: 20 PPI Filter sponge.
Tray 2,3,4: All 3 of them are filled less than halfway with Seachem Matrix.
Top Tray: Bag of Seachem Purigen.

Once filter is optimised as above and if flow in the tank not improved, next on list is number of holes in spraybar and size, less holes and/or smaller hoes will create more of a jet action, the jet action is due to the water leaving the holes at a higher velocity and will have more energy, this higher energy will create more flow in tank, yes the output from filter will be less, but will create more flow/turnover and flow is king. You could try taping up half the holes to start with.
I did experiment with taping up some of the holes.
The first thing I tried was using only 1 half of the spray bar, rather than the 2 pieces connected, but I found the flow was actually too much this way. The plants were moving around a lot and the fish didn't seem to appreciate it either.
Next, I went back to the full length spray bar and taped up every other hole, ending up with the same amount of holes as when using half the spray bar, but spaced out across the entire length of the tank, rather than just the center.
The result was very similar to the first test with half the spray bar.
After that, I started removing the tape from the holes one by one (While keeping it symmetrical of course), checking the flow each time a hole opened up, but once all the tape was off, none of the things above solved the problem.

Any of the options I've tried have created the same problem.
The flow rate itself isn't really a problem. With the full length spray bar, all holes open, I get a nice flow with most of the plants lightly moving back and forth. When taping up some holes, I can get it strong enough to really move the plants a lot, and then I can reduce the rate on the filter itself.

The problem (At least I think it's a problem) is that the flow goes in different directions at random places in the tank.
If I look at the surface from above, the left half is going in a counter-clockwise circle, the right half is going in a clockwise circle, then there are a couple smaller circles doing the same at random places, almost like a bunch of cogwheels.
Then there's also a few places where the flow is going in a straight line, rather than a circle, either going from front to back, or back to front.
Keep in mind, all of these different directions are still only just the movement of the surface.

Then, when looking at the tank from the front, there's too many things happening to give a clear description.
There's points where the flow goes upwards, points where it goes downwards, to the left, to the right, etc.
These different directions are not really separated, where one bigger area goes upwards, another big area goes downwards, etc.
There's quite a few spots where you can literally see the different directions right next to each other. Going downwards, then not even a cm to the left it goes upwards, etc, etc.

I don't have a clue how this is happening and why the flow doesn't go forward out of the spray bar, down the front glass, across the substrate and back up again.


When tank is half full of water at WC and filter is on how far does the water go from the spraybar?, ideally it should reach the front.

Ideally the CO2 bubbles should be jetted to the front of the tank and right down to the substrate level.

Getting the flow right at first will pay off later esp when the plants fill, as they will reduce the flow and thats when the plants may suffer
I need to do my weekly WC tomorrow, so I'll take a video of the jets once the tank is half full and will post it here.
The CO2 diffuser is right next to the inlet at the moment. About half of the bubbles are being sucked into the filter and the other half gets blow to the front of the tank and down to the substrate.


I agree with Karl. The next step is to remove about 2/3rds of the filter media, especially the silly rings or hoops, which are specifically designed to slow the flow so that large debris can settle out and get trapped.

Cheers,
I'm quite light on media already, and those rings (Hel-X) went into the bin the second I opened the filter for the first time. 😝 I'm using Seachem Matrix instead. All the details regarding my filter layout are mentioned above.
 

Dogtemple

Member
Joined
22 Nov 2011
Messages
134
Location
Brighton
I'm curious about this removing filter media suggestion.

if removing it surely that only increases the volume of water in the set up.

if that's the case, what would be the choice of media to optimise the filter in a planted tank?
 

Zeus.

Fertz Calc Meister
Joined
1 Oct 2016
Messages
3,925
Location
Yorkshire,UK
I'm curious about this removing filter media suggestion.

if removing it surely that only increases the volume of water in the set up.

if that's the case, what would be the choice of media to optimise the filter in a planted tank?
bio media for fluval 305 gives a good place to start
 

Nick potts

Member
Joined
25 Sep 2014
Messages
602
Location
Torbay
I'm curious about this removing filter media suggestion.

if removing it surely that only increases the volume of water in the set up.

if that's the case, what would be the choice of media to optimise the filter in a planted tank?
The main benefit is more flow through the filter, and therefore the tank.

A well-planted tank doesn't need a lot of biofiltration and sponges could easily cope. Of course, things are different in highly stocked or low/no plant tanks.
 

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