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Connecting a Tidal 55 to an undergravel filter, 29 gallon tank


Sep 6, 2020
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United States
My logic for this project, I always vacuum the gravel when making water changes. So cleaning a gravel filter adds no additional work. But Aquarium Science says I shouldn't vacuum. Anyways, this now gives me the best of both worlds. I now have a low maintenance undergravel filter with a huge bio and mechanical filter and can use the Tidal filter basket for whatever I want.

I agree with the Aquarium Science article, the arguments against UGF when using gravel substrate just don't make sense. Now using fine grain sand vs gravel is a different topic open for debate.

Now the good news, the water intake tube fits perfectly inside a piece of 1" PVC pipe! That's makes this a easy project. The bad news, the inside dimension of sch 40 PVC pipe is not standardized. I suggest taking the intake tube to Home Depot to make sure they fit. So an easy way to make a DIY UGF filter, connect a 1" PVC pipe, 1" coupling, 1" to 1/2" bushing, 1/2" tee shown below.


I suggest only using perforated pipe on the blue pieces of pipe to get a more even flow but this is just speculation on my part. Long term the screen material may be a bad idea, it could get plugged up. Only time will tell.

Of course I did it the hard way, I connected the 1" pipe to a small PVC box. The 1/2" PVC pipe is connected to the box shown below:


On my tank, the Tidal is mounted on the side. The long term goal is real plants along the back and side. The gravel you see is actually Eco-complete with a thin layer of gravel on top. There is 2.5"perforated pipe buried in the Eco-complete, I wrapped screen material around this pipe. The logic here, create a slow flow of water thru the planted section which will not be vacuumed. You can't see it here but screen material covers the entire bottom.

Note: the round 2" piece of pipe is for another plant ie: a planter box.

I used my table saw to cuts the holes in the shown below:


Of course you can just drill holes instead.

And here the final results:

Tidal Mod.jpg

I did a simple water flow test with the Tidal connected to the UGF vs unconnected, I measured little difference in flow. Note: I did block the skimmer water intake on the bottom with silicone.

I am quite happy with this project,. Being semi-retired, I need aquariums that can run with little supervision for a couple weeks at a time in case my wife and I make a trip. I can use the Tidal just as a water pump and this should be a very reliable system requiring little maintenance. I think this is a better option than using power heads, I can still use the Tidal as a filter.

Next mod for this system, an effective way of putting Polishing Felt Filter Pad 100 Micron in the Tidal filter chamber. Shown below is a air filter:

air filter.jpg

With the zig-zag pattern, they can double the surface area of the filter material. How can I do the same with the felt polishing material?


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