Hi everyone, my name is Roger and I love this website. Long-time reader but first-time contributer, so please leave plenty of questions, comments, and feedback at the end :)

I recently started keeping freshwater fish in an aquarium which came with an Aquaclear 30 Hang-on-Back (HOB) power filter. While the filter works fine, I noticed that a lot of the clean water that flowed out went straight back into the intake tube to the left (I keep the set the flow to low since I have slow-moving fish.) So basically, the HOB would continually refilter the same small amount of water while leaving the rest of the tank water uncirculated and dirty.

In my mind, there were two possible approaches to this problem. I could shift the filter to the right of the tank and extend the intake tube horizontally to the left with some PVC joints and tubing. Or, I could move the filter to the left and make something to divert the clean water flow to the right, away from the intake tube. Fortunately, the decision was made for me: moving it to the right would've covered some light switches, so... "to the left, to the left!"

This project is quite simple and offensively inexpensive. By the end you should have an efficient, barely noticeable trough that funnels the water away from the intake tube, thereby circulating the aquarium water. Your fish will love you for it!

Here's some photos of a prototype I made. You probably already have a sense of where this project is going just by looking at it:

Step 1: Things You Will Need

1. HOB filter that works
2. Tape measurer
3. Sharpie Pen
4. Hobby knife
5. Shears or strong scissors (depending on how thick your cup material is.)
6. Smaller scissors for more precise cuts
7. A good pair of eyeballs (preferably your own) for eyeballin' measurements
8. Plastic cup (several for trial-and-error)

There is a mindboggling variety of plastic cups in the world, so which one is right for this project? It's really your call.

In general, what you're looking for is a relatively inconspicious cup so it won't detract from the look of the tank (unless you want a 7-Eleven Big Gulp monstrosity to be the focal point of your aquarium!) Clear plastic is preferred since it's durable and see-through. As for size and thickness, it depends on your filter. Mine is just a wimpy Aquaclear 30 (the second weakest of all Aquaclear HOBs), so I did not have to worry too much about the water flow overpowering and bending the cup as it diverts water. If your filter has a greater output, then you should look for a sturdier cup.

The cup material should not be brittle since we'll be bending and contorting it to stay in place under the HOB. It should also be tall enough to catch the whole "waterfall" of clean water from the filter (mine was 3 1/4 inches.) It would also be helpful if the cup has a reinforced lip to bear the weight of the water. Oh, and remember to clean the cup thoroughly so you don't infect your fish with cooties or alcohol poisoning :)

I know, all this fuss over a stupid cup. Don't worry, it'll all become clearer as the project progresses. I just happened to find a stack cheap ones under the sink. They're kind of like the ones your dentist gives you to gargle with after invading your mouth. Perfect.
I know this is years old but, I'm not sure what size your tank is but if it is possible for the water from the filter to be sucked back in the intake you don't have one of the following. A. The right size filter for your tank (there is no such thing as over-filtration, but under-filtration will result in a dirty tank and a plethora of other issues) <br>B. Your down tube is too short. This type usually comes with at least two, connectible tubes. If it is too long using both, cut one of them shorter and fit it back together with the supplied connector. The bottom of the down-spout should be at most few inches from the bottom of the tank unless you have a very deep tank like a &quot;Tall&quot;. Just trying to be helpful to those that might read this, I've had 4 or 5 of these over the years and always had excellent luck with them.
great instructions, but cutting the cup so its angled and partially in the water means direct water contact without the waterfall effect. Attaching a small sponge or clear plastic piece with some holes will prevent fish from climbing onto it.<br />
I have a great use for this. In one of my tanks I only have shrimps/crayfish. They're feeders, I also have plants and some duck moss (I think that's what it's called). The duck moss is small little floating peddles/leaves and when it grows in thick enough the filter starts shoving it directly down into the intake, where it gets stuck on the grill or sucked into the filter, obviously clogging up my filter. Now I want the duck moss, my koy LOVES it, so I grow it for him, but I hate having the remove the filter every other day and scrapping it off. After I did this cup mod the water now jets to the right, blowing the duck moss under the water to the right away from the intake. I haven't seen the moss in my filter for 4-5 days now, and don't expect to. Great mod!&nbsp;Great instructable, the only complaint I&nbsp;could possibly have is it does look tacky, but then again this was for my breeding tank that's in my basement so....<br /> Also, I'm going to try this out on a bigger tank&nbsp;I have, just because the filter is noisy when pouring the water into the tank and it's in my bedroom, I think that this will reduce that noise, thanks again!<br />
I do not see a point for it ... sorry I keep fresh water planted tanks and I do have this filter, it works great even on a low setting. Never have a problem with dirty tank my water is crystal clear. If you think the water coming out goes straight back into the initake tube, it doesn't also placing an air stone will help ciculate the water. If the flow is a bit too much for your fish put a sponge in the intake tube which will prevent fish from getting sucked into it. I also don't like how the cup looks, all my tank are open tops and it won't look good. IMHO if the filter doesn't work the way you like it get a bigger one, I believe in over filtration. Anyway a good idea for some but I think it's pointless...
im missing the point of this... it could be that im half asleep as i always am while using the web... or just plain me... my filter is exactly like that.... what is that cup doing(otehr than being there and looking kinda cool..)
Great idea! You've inspired me to make a big one for our double-bayed HOB filter. I will noodle around with some 2-liter pop bottles and see what I come up with.
It would also help some if you extend the intake tube down so that it sits about an 1" above the bottom,. by cutting the stock tube just below the waterline and going to Home depot and get some clear spa hose/tubing (the right diameter), measure to length, cut, heat in hot water to make plyable, straighten it and fit on filter and end . Done!!! and you don't have that black tube hanging down in your tank.
Awesome-fied! Hence, the reason I always hated HOBs. I"ve recently picked up 2 that came with 2 55s I got and this is going on both. Thanks! 5 stars!!
thats really smart !! i have an old aquaclear 200 (now its called 5)) and a newer 70, i will be doing this with the 50 since i have a powerhead in the same tank as the 70 :) great idea!!
Thanks for the positive comments, I'm glad people are finding this instructable helpful :)<br/><br/>I tried using a long plastic bottle today and found it not as easier to work with. Once I have some more time this summer I'm going to look for the gutter material used for draining rainwater on homes and give that a try. <br/><br/>Extended waterfall + Added biological filtration + More secure attachment = WIN!<br/>
Great idea! I think I'll try this with my filter. I'm not pleased with how the expelled water seems to be sucked back into the filter right away.
Incredibly detailed instructable about an incredibly simple fix for an incredibly obvious problem! INGENIOUS! 5 stars from me, keep up the good work and hope there's more ibles to come! Great job again!
Nice photos, I made one of these a while back out of a 1/2 gallon milk container and used aquarium leak sealer to attach to the filter.

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More by rgrling:The Tower of Filtration: (Yet Another) Air-Driven Aquarium Filter How to Awesome-ize Your HOB Power Filter with Just a Plastic Cup 
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