Water flow and water line.

Dave125g

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I wanted to talk about how your water level affects your filtration with an HOB. With the water line above the filter output your filter operates much more efficiently. It's also quieter. By contrast, with the water line below the filter output your filter is basically filtering water that was just filtered. Leaving 3/4 of the tank water unfiltered. For those who say I need the oxygenation, I say get an airstone. For those who say "I like the waterfall sound", I say buy a waterfall decoration. So, for the health of you aquarium fill your tank.
20191031_110709.jpg
 

mattgirl

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YASSSSS!! Visible waterlines make me crazy too.
Me too !!!! my 55 is about 1/4 inch lower on the right side so I have to live with a tiny water line. I have learned to live with it but wish it weren't so :( But I always keep my tanks filled high enough to keep the HOB's output below the water line.
 
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Dave125g

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Yes I don't like to see the water like. It's an eyesore. It looks like your too lazy to top off your tank. But more then that it's not healthy for your tank.

Me too !!!! my 55 is about 1/4 inch lower on the right side so I have to live with a tiny water line. I have learned to live with it but wish it weren't so :( But I always keep my tanks filled high enough to keep the HOB's output below the water line.
It's tough to level the stand. As accurate as you get it, it changes when you fill the tank.
 

mattgirl

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It's tough to level the stand. As accurate as you get it, it changes when you fill the tank.
Right. when hubby set this one up for me he got it as level as possible. He is a perfectionist so got it perfect but once filled it changed :( Fortunately the stand is perfectly flat so the tank is well supported. The 1/4 inch difference should never cause a problem other than a small eyesore.
 

Cichlidude

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Of course if you place your HOB between the 1/3 and 2/3rds mark in your tank it will do much better than at the left or right side.
 
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Dave125g

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Of course if you place your HOB between the 1/3 and 2/3rds mark in your tank it will do much better than at the left or right side.
Yes mine always go in the middle. I didn't think about that in my drawing. Thanks for pointing that out.
Although that's not the point I was trying to make.
 

ForceTen

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Me too !!!! my 55 is about 1/4 inch lower on the right side so I have to live with a tiny water line. I have learned to live with it but wish it weren't so :( But I always keep my tanks filled high enough to keep the HOB's output below the water line.
Have you considered leveling it? I am OCD about stuff like this and would be hard pressed for a good nights sleep with a tank thats not level.

You could do a major water change. Take out any heavy objects and be able to easily level the aquarium.
My wife has these sliders that go under furniture so they can be moved around easily. With the sliders came a lifting tool. Its designed to lift the furniture to put a slider under.
Its perfect for this and a 55g with not to many heavy rocks could be leveled by one person. Two people are much better.
 

Cichlidude

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Yes I don't like to see the water like. It's an eyesore. It looks like your too lazy to top off your tank. But more then that it's not healthy for your tank.
Well what folks can do is fill the tank to where you want it. Then simply grab some black electrical tape and go around the outside to mark the level just below what you want. Now when the water level drops a bit... it looks perfectly level.
 
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Dave125g

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Have you considered leveling it? I am OCD about stuff like this and would be hard pressed for a good nights sleep with a tank thats not level.

You could do a major water change. Take out any heavy objects and be able to easily level the aquarium.
My wife has these sliders that go under furniture so they can be moved around easily. With the sliders came a lifting tool. Its designed to lift the furniture to put a slider under.
Its perfect for this and a 55g with not to many heavy rocks could be leveled by one person. Two people are much better.
Water weighs about 10 pounds per gallon add that to the weight of the substrate, tank and stand. What your suggesting is near impossible and very dangerous. Only safe way is to remove every thing, sure up the low corner and refill. If your lucky it only needs to be done once.


We're starting to get off topic. I created this thread to explain the relationship between water level and filter performance.

Well what folks can do is fill the tank to where you want it. Then simply grab some black electrical tape and go around the outside to mark the level just below what you want. Now when the water level drops a bit... it looks perfectly level.
Yes but I just top it off. Seems a bit easier.
 

ForceTen

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Water weighs about 10 pounds per gallon add that to the weight of the substrate, tank and stand. What your suggesting is near impossible and very dangerous. Only safe way is to remove every thing, sure up the low corner and refill. If your lucky it only needs to be done once.
We're starting to get off topic. I created this thread to explain the relationship between water level and filter performance.
I thought water was 8Lbs per gallon? Minor leveling adjustments are indeed possible and I am doing it right now.
I have 100Lbs of sand and three inches of water in my new 40g tank. I am leveling it with weight in it because its more accurate and more reliable. Lush carpet with thick padding is the issue for me. A hard floor makes this job easier, but leveling a tank on carpet is not as easy as some may think.
While leveling with nothing in the tank is the best bet, its not always possible and in many cases its not good enough
 

Momgoose56

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I wanted to talk about how your water level affects your filtration with an HOB. With the water line above the filter output your filter operates much more efficiently. It's also quieter. By contrast, with the water line below the filter output your filter is basically filtering water that was just filtered. Leaving 3/4 of the tank water unfiltered. For those who say I need the oxygenation, I say get an airstone. For those who say "I like the waterfall sound", I say buy a waterfall decoration. So, for the health of you aquarium fill your tank.View attachment 632138
Okay! Interesting! I have to say, I don't care to hear my filter splashing but as your incredibly steady handed depiction shows, the 'waterfall effect' also creates additional surface turbulence and increased water oxygenation. Plus, have you tested your water flow theory with some sort of semi-buoyant small object that will actually follow the flow of water from the outlet? What I would recommend is that people adjust the level od water in their tank with a HOB filter, to the particular needs of the tank.
What I think actually happens, knowing some fluid mechanics, is that the resistance of the surface water to water falling on it would spread the flow out more at the surface level as opposed to water, entering water without that resistance which I think, would slow and spread out further down (maybe halfway) in the tank. Water is a great cushion. That's why ballistics testing involves shooting bullets from above into a tank of water. Any bullet will come to a dead standstill within a few feet of the surface. A more dramatic example of how resistant water is: If you jump from a 30 foot cliff and land in the water flat on your rear end, you're not only going to have bruising on your rear and posterior thighs, but you might have shock/impact injury all the way up your lower spine. Just my educated ruminations...what do you think?
 
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Dave125g

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I thought water was 8Lbs per gallon? Minor leveling adjustments are indeed possible and I am doing it right now.
I have 100Lbs of sand and three inches of water in my new 40g tank. I am leveling it with weight in it because its more accurate and more reliable. Lush carpet with thick padding is the issue for me. A hard floor makes this job easier, but leveling a tank on carpet is not as easy as some may think.
While leveling with nothing in the tank is the best bet, its not always possible and in many cases its not good enough
Yes 8.2 pounds per gallon. I use 10 because it's easier to multiple. Moving a tank with water in it can cause seals to fail. You can level your tank with water if you want. But I would rather not have 125 gallons of water flooding my living room.

Again this is off topic.
Okay! Interesting! I have to say, I don't care to hear my filter splashing but as your incredibly steady handed depiction shows, the 'waterfall effect' also creates additional surface turbulence and increased water oxygenation. Plus, have you tested your water flow theory with some sort of semi-buoyant small object that will actually follow the flow of water from the outlet? What I would recommend is that people adjust the level od water in their tank with a HOB filter, to the particular needs of the tank.
What I think actually happens, knowing some fluid mechanics, is that the resistance of the surface water to water falling on it would spread the flow out more at the surface level as opposed to water, entering water without that resistance which I think, would slow and spread out further down (maybe halfway) in the tank. Water is a great cushion. That's why ballistics testing involves shooting bullets from above into a tank of water. Any bullet will come to a dead standstill within a few feet of the surface. A more dramatic example of how resistant water is: If you jump from a 30 foot cliff and land in the water flat on your rear end, you're not only going to have bruising on your rear and posterior thighs, but you might have shock/impact injury all the way up your lower spine. Just my educated ruminations...what do you think?
On topic. Thanks for the ballistics lesson, and the complement. I do think your comparing apples to oranges though.

I addressed oxygenation in the first post. In addition to an airstone....live plants are really all you need. But if your not into that, an output below the water line provides enough surface agitation. If not I'd say your under filtered.

As far as a test. Not exactly. I'm not a scientist so I haven't used a proper scientific method. However I keep Italian vals. I have observed there movement with the water line both above and again below the filter output. That's how I came to my conclusion. You may call it a hypothesis if you wish.
 

Cichlidude

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You have to consider the HOB also. Almost all HOBs with the exception of the Tidal filters have a sharp drop off. The Seachem Tidal filters have an extended outflow to push the water across the tank instead of dropping it straight down into the tank.
 
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Dave125g

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You have to consider the HOB also. Almost all HOBs with the exception of the Tidal filters have a sharp drop off. The Seachem Tidal filters have an extended outflow to push the water across the tank instead of dropping it straight down into the tank.
I didn't consider cheap HOBs. The aqueon HOBs don't have that straight down output either. That's a good point. If you have 1 of those filters it doesn't matter where the water line is. From a filter performance perspective, that is.
 

Magicpenny75

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In my 75 I have an AC110 hung on the right side end of the tank. When the tank is full up I get zero surface scum, no bubbles in the water, and just a quiet riffling of the surface right at the bottom of the filter output and traveling about 2/3 across the tank. I can tell there is more surface movement because I have 2 COB LED gooseneck lights (no lids), and when the tank is full the reflection on the ceiling shimmers like crazy. When the water level drops, there is a very distinct (annoying!) bubble pattern beneath the filter output, and the lower the water gets, the bubbles are angled more steeply down and don't travel as far out into the water column before returning to the surface. The reflection on the ceiling also gets calmer at the other end of the tank. Also, if I leave the water level low for a couple of days, there is the beginning of the surface scum at the end of the tank opposite the filter. So for those reasons I always try to keep it filled up. I haven't done anything specifically scientific, those are just my observations. I'm sure that the water isn't only moving in a little circle right in front of the filter, but the turbulence certainly seems more localized and things move less at the other end when the water is low.
 

Momgoose56

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Yes 8.2 pounds per gallon. I use 10 because it's easier to multiple. Moving a tank with water in it can cause seals to fail. You can level your tank with water if you want. But I would rather not have 125 gallons of water flooding my living room.

Again this is off topic. On topic. Thanks for the ballistics lesson, and the complement. I do think your comparing apples to oranges though.

I addressed oxygenation in the first post. In addition to an airstone....live plants are really all you need. But if your not into that, an output below the water line provides enough surface agitation. If not I'd say your under filtered.

As far as a test. Not exactly. I'm not I scientist so I haven't used a proper scientific method. However I keep Italian vals. I have observed there movement with the water line above and again below the filter output. That's how I came to my conclusion. You may call it a hypothesis if you wish.
Well, that makes sense. You would see more plant movement with water movement spreading out below the surface and not so much with water spreading out on the surface. This is how I think the water would move:
20191031_104638.jpg
Sorry, i'm right handed but it works worse than the other one now so I've had to learn to write left handed- pretty sloppy!
I'll test it the dual "hypotheses". I have a 30 g with a HOB that needs a water change. I just have to find something that is semi buoyant around the house...Mung beans maybe? Dried garbanzos? lol! I LOVE experiments! I'll see if I can video the results but i'm going to have to ask how to post one. I've never posted a video before...:rolleyes:
 
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Dave125g

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Well, that makes sense. You would see more plant movement with water movement spreading out below the surface and not so much with water spreading out on the surface. This is how I think the water would move:
View attachment 632172
Sorry, i'm right handed but it works worse than the other one now so I've had to learn to write left handed- pretty sloppy!
I'll test it the dual "hypotheses". I have a 30 g with a HOB that needs a water change. I just have to find something that is semi buoyant around the house...Mung beans maybe? Dried garbanzos? lol! I LOVE experiments! I'll see if I can video the results but i'm going to have to ask how to post one. I've never posted a video before...:rolleyes:
Your drawing depicts a filter output pointing straight down. Is that how yours works?

Post your video to YouTube then post a link here.
 

Momgoose56

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Your drawing depicts a filter output pointing straight down. Is that how yours works?

Post your video to YouTube then post a link here.
It's a HOB. The water falls straight down, like a waterfall, as with all HOBs I thought... i see what you're getting at though, if the outlet is below surface level, the water would dissipate outwards faster, rather than straight down. Right! My drawing doesn't take that into consideration as yours does! I'll do the experiment sometime today and post tomorrow
 
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Dave125g

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It's a HOB. The water falls straight down, like a waterfall, as with all HOBs I thought... i see what you're getting at though, if the outlet is below surface level, the water would dissipate outwards faster, rather than straight down. Right! My drawing doesn't take that into consideration as yours does! I'll do the experiment sometime today and post tomorrow
No. Quality HOBs have an output that goes across the top. That was discussed a few posts back.
 
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