Gravel Vac - doesn't pic up waste - The Planted Tank Forum
 
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post #1 of 8 (permalink) Old 09-02-2014, 03:40 PM Thread Starter
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Gravel Vac - doesn't pic up waste

So ever since I set up my main tank 6 or 7 years ago I've bene using the Lees Ultimate Gravel Vac, which is pretty much exactly like a Python. I always thought it was doing a good job - when I stick it down in the gravel it pulls up tons of mulm and whatnot which looks like tiny bits of dust when it comes up thru the vac.

However, I recently set up a bare bottom hospital tank and the exact same vac doesn't seem to even have enough suction to suck up individual bits of fish waste and I end up having to use a regular gravel vac and a bucket on this tank, which is very annoying.

Is there any way to increase the suction on a Python type vac? Is it a problem of low water pressure or something?
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post #2 of 8 (permalink) Old 09-02-2014, 04:43 PM
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What provides the "power" for siphons is the height difference between the water surface level and the end of the tubing where the water comes out. Same way the tap water pressure is controlled in many cases. If the new tank water level is lower than in the other tank the flow will be less.
A way to speed it up is to have the new tank higher or lower the end where the water comes out.

To get more apparent "power" by increasing the velocity of the flow, you can use a smaller pickup tube in the tank but keep the same size output tubing. If you have a 2" tube as the pickup, a cap with a smaller diameter will increase the velocity and make it appear stronger.

Last edited by PlantedRich; 09-02-2014 at 04:47 PM. Reason: add
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post #3 of 8 (permalink) Old 09-02-2014, 04:51 PM
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If you hold the intake really close to the floor of the bare bottom tank it will pick up better. They will even suction themselves to the floor of the tank. Easy to remove, just annoying.

I finally put my finger over the end just enough so it could not snap down onto the bottom of the tank.
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post #4 of 8 (permalink) Old 09-02-2014, 06:28 PM Thread Starter
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This new tank is maybe 3 inches lower to the floor than the other one - both are tall tanks. I do hold the intake directly over the waste - like right on it - it floats up a few inches then falls back down.

I'll see if I have a smaller intake tube around here. I like the one that came with it because it has a claw on it, so if a fish gets too close it's impossible to suck it up.

Also, right now I have a long run from the sink to the tank - no way around that. Alot of the hose lays on the floor. Will it help the suction at all if I get the hose up off the floor? Maybe set up some dining room chairs for it to lay on instead?
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post #5 of 8 (permalink) Old 09-02-2014, 06:53 PM
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No noticeable change in moving the hose middle hose higher. No chance of a shower close by so that the end would be lower? Dropping it out in the yard and lower is nice but that can have some big problems if you have folks coming and going.
A bare bottom tank that is pretty small? Can you get the larger tube off the small tubing and just use the tubing end to pick up? Same amount of liquid going through a smaller hole makes it look faster and pick up heavier stuff.
One of the better finds I've made is a syphon with a grid on the end so that anything larger than an 1/8 " gets filtered out. It must be a Chinese import and I've never found a place to buy one. Japanese, Korean , nor Vietnamese are able to read the writing.
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post #6 of 8 (permalink) Old 09-02-2014, 07:55 PM Thread Starter
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It's a 20T and is bare bottom cause it was set up as a hospital tank. I'm actually gonna keep it set up for the angel that's in it and add gravel. I guess my biggest concern is that all this time I thought I was vac'cing up the fish waste in my other (main) tank and now I'm wondering if I've just been picking up gravel dust/debri and bits of snail waste and leaving the bigger stuff behind. In a gravel tank you really wouldn't notice it if that was the case because the fish waste falls down in the gravel and disappears. I'm rethinking my entire maintenance routine now cause of this!
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post #7 of 8 (permalink) Old 09-02-2014, 10:18 PM
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When you stick a gravel vac down in the gravel you restrict the opening (with substrate) which increases vacuum pressure. You can't get the same kind of pressure increase in a glass bottom tank since the 1 variable to increasing said pressure is missing... The gravel. Get some kind of flow restriction on the end of the vac or remove the gravel vac part of the assembly and just use the 3/4 inch line to suck out the waste in question.

Also fish waste starts to decompose when expelled, ever watch a shrimp pellet disintegrate, same thing only slower than your eye can perceive. This in turn adds to the mulm that is vacuumed from the tank.
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post #8 of 8 (permalink) Old 09-03-2014, 02:04 AM Thread Starter
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Thanks everyone.
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