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To be fair, the author of the Aquarium Science article included: A Caveat Undergravel filters have not been widely tested as a filter in the aquaculture industry, The limited testing done on gravel filters for aquaculture was “all over the map” due to the very high loading of commercial operations. So one is left with common sense and anecdotal “testing” as the only sources of information in the analysis below. So the question of should I vacuum the gravel is open for debate. For myself, I will vacuum the open areas every water change, it is so easy with my setup. The debate on UGF is should be: sand vs gravel substrate. If using gravel (~4 mm in size), detritus will settle into the gravel and may require cleaning. So just put in an UGF.

Get a cheap water pump from Amazon, put it in a bucket and cover it with gravel. Run a hose from the water pump back into the tank. A water pump with an intake on the bottom would be best. Use a siphon gravel cleaner to suck up crap in the tank, dump the water into the bucket, pump it back into the tank. If you have a dolly for the bucket or an old cooler with wheel, use that.

One more issue with this system. The Tidal mounted on the side created a serious current in the tank. My original plan was to create a river tank but that didn't work out. Connecting the Tidal to an undergravel filter has reduced the current, I can now run the Tidal near full output.

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: 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: 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?

Absolutely! Big thanks to you and all for your excellent feedback. It seems to me for CPD, go big (large school) to dominate the tank or let them be little treasure fish ie: you have to closely observe the tank to see them. I am OK with the latter, I decide I want a community tank. So I may just get 8 CPD (One grip against buying from Aqua Huna, have to buy in multiple of 8). I was thinking about Von Rio (flame) or Emerald Tetra, possible Serpae or Candy Cane Tetra with the CPD. The Serpae may be a problem.

Yep, I need to figure this out. I have never setup a nano tank , I forget how many you can put in a 29 gallon tank! I have a Tidal 55 mounted on the side which can create a serious current, was thinking about a river system. That didn't pan out and I connected the Tidal to an undergravel filter which should dampen the current and I can just turn the flow down on the Tidal. I'm leaning toward 16 CPD and possible 2 schools of Tetra's but that seem like alot of fish in a 29 gallon tank.

The forktails are always out and about. There are currently in a 20 gallon grow out tank. Cory stressed the important of dither fish for the Celestial Pearl Danio, just wonder if I need more.

Thanks! The best I can do is 16 but I may lose a few in shipping. I currently have plastic plants and can create a jungle along the back. Will have to think about this purchase. I love the look but don't want a where the fish tank. I only have 5 Forktail rainbow, maybe if i add some laid back tetra will help out.

So below is the picture everyone uses, I believe this is a male in full breeding colors. How far off are their normal everyday colors?

I have a 29 gallon tank with 6 Panda cories and 6 Forktail Rainbow (need more of these guys). So would a school of 16 Celestial Pearl Danio be enough to get them out from hiding? I have dither fish on the bottom and top of the tank but as I said, may need more Rainbows. I would be disappointed if I bought these guys and they just hide in the plants all the time. Opinions?

Nice to see someone else creative with materials! So if making something a couple inches thick with silicone/substrate, will the silicone cure in the middle? Should you use damp substrate to provide moisture? Something else I want to try, mixing spray foam with substrate. Of course that would be quite messy but curious if you could build structures with it.

FYI, from the mold making world. Mixing in a little vegetable glycerin to the silicone will help curing thick application of it. Glycerin is a humectant which attract moisture required for the curing of silicone which you most likely already knew. Of course that raises the question, is Organic Vegetable Glycerin for skin care safe for fish?

I got lazy and for aesthetic reasons, I put the overflow box and water return lines from sump on the same side of the tank. As I should have expected, I got poor circulation in the tank. So while I have a spare tank around for a temporary home to the fish, I was thinking about connecting the sump return lines to a DIY undergravel filter. The sump has a fluidized bed filter and filter socks, I really don't need more filtration but it can't hurt. The primary goal is to improve water circulation, a constant slow flow thru the gravel up to the overflow boxes. Would this be beneficial to plants? I did read Why did the under gravel filter lose popularity? and tend to agree, undergravel filter work great. With sumps, HOB or canister filters, detritus will still settle into gravel substrate. Sand is the solution to keeping your substrate clean. So if using gravel, an undergravel filter seems like a benefit to me. On my 29 gallon tank, connecting the Tidal HOB filter to an undergravel filter may be a future project. EDIT: For a planted tank, I could just add the undergravel filter to the front of the tank ie: areas with no plants.

Thanks for your reply. What I may do for future projects using this glue, cover it with silicone and whatever subtrate you are using.

I believe J-B Weld WaterWeld epoxy putty is safe for aquariums.

Big thanks for all your work. Specifically for this one, the company Gorilla Glue makes different products including a version of super glue. But what about their main product, the moisture activated polyurethane adhesive? The SDS (?) data sheet says it is toxic to fish. But many other have said that once fully cured (~ 1 week), it is inert and safe for aquariums. My opinion, moisture activated polyurethane works better than silicone when mixing with substrate for hardscape projects. Mix together with damp substrate then cover it with regular substrate as it cures. Here is an example of a cave I made. I used a balloon filled with sand as a mold, a white sand & polyurethane and cover it with gravel.

I did notice that, well done and a toast to PVC! I built a sump filter/overflow boxes with PVC material from Home Depot.

Nice tank! I see a canister filter, what are those 3 pieces of PVC pipe hanging in the tank? Is that a DIY project or something you bought?

Nope, I just misted them with water before taking a picture. This is for a 75 gallon Mbuna tank, I plan on stocking it with 4 colonies of Mbuna, 6 per colony (a total of 24 fish). the substrate will be white aragonite. so what are your plans for your tank?

Understood, that make sense. I just suggested the plywood if you are concerned with cracking the bottom of your tank from the weight of the rocks. If you got some huge rocks going in, put them in the corners of the tank to reduce the load on the glass. Gotta love free rocks which can be hard to find for many of us. I got mine from a construction site along a high voltage transmission line right-away. No worries about nasty chemicals like round up, it's just overgrown weeds. This is the latest layout in my project:

I missed that line, an old tank may not have tempered glass. If you can put a plywood sheet on top of the stand, I suggest this. Put some clear package tape on the plywood then apply a thick bead of caulk to it. Then set the aquarium on top of the plywood before the caulk dries. The caulk should help support the bottom. If you need to remove the tank, the caulk should not adhere to the tape. You could also put the tape on the bottom of the tank, same idea.

This guy from KG Tropical put ~600-800# of rock in a 240 gallon tank, tempered glass is very strong. The standard advice other have mentioned, put a egg crate ceiling light panel on the bottom to eliminate pressure points and to distribute the load. I Built The PERFECT Tank For Cichlids, Yellow Lab Aquascape Another suggestion I have, using silicone caulk, attach a piece of PVC pipe to the bottom of the tank. Now set the rock on top of the PVC pipe. If you have fish which like to dig, no chance the rock will come crashing down on them. And this makes cleaning under the rock much easier, no need to dig the rock into the substrate. I did something similar for smaller rocks, I glue the pipe to the rock: No, that's not a potato! It's a rock! End results: So the rocks stay in place in the sand substrate. EDIT: I plan on putting ~150# of rock in a 75 gallon tank.

Just an update, I finally back on this project. Here is a general layout of the rock structure I will be using. Not shown is this photo, the supporting PVC structure to hold the rocks and create the condo, thats next on my agenda. So the rocks are laid out in a semicircle, there is a open space on the front and side walls. The gap you see between the rocks will be the entrance to the condo which are under the rocks. This whole structure will be ~3-4" off the bottom of the tank. Common feedback I am getting from many... When a male Mbuna goes rouge and start terrorizing other Mbunas, I should not expect that the terrorized Mbuna will or can hide in a condo to getaway. My current design is a 3 story condo complex where us human would claim a condo for protection. This may not work with fish 🙂. So does using all the space for 26+ condo really make sense? So what I can do. In the mold I made to build this, pack sloping sand along the front and sides shown below: The sand acts as a mold for the expanding foam, the opening you see here under the rock will be foam. So this will create a ledge surrounding the rock structure for the condos. Kinda like a moat around a fort. I hope this helps in the line of sight issue, a terrorized Mbuna can swim under the ledge to get away from a rogue male. So the bottom line, this will reduce the number of condo's but create a common space where I hope any Mbuna can hide out. Any thoughts will be appreciated.

Yes we do and thanks so much for that link! Finally someone else gets it, make a Lake Malawi tank ie: all rocks! I also have the same problem as John, finding rocks and I need more rocks! I did find a bunch of black rocks, may go back where i got them for more. I did start a journal last year, here the link: Mbuna Condo Below is the look I am going for: So the bottom layer of rocks are set in a layer of foam. This is version 1 of the PVC condo structure, I am currently working on version 2. So concept here is, stuff a balloon filled with sand in all the condo then stack a layer of the base rocks. Then pour foam on the whole frame. Then of course remove the balloons. What John says is so true, trying to find the right combo of rocks stacked to make a cave is very difficult. So I am cheating.... Thanks for the tip! I plan on using Great stuff foam as a base filler then 2 parts pourable foam (3# density) I got from US Composite. All the foam will be coated with white silicone caulk covered with aragonite substrate. The US Composite foam is for marine application.

Much more complicated. Under the rocks will be caves (I am calling them condo's) built using PVC material for the Mbuna. The rocks will be held up by a bed of foam (a combo of great stuff and 3# density polyurethane foam). The goal is to get 22-24 condo's in the tank. The pourable foam will also create a slope effect. So adding buoyancy is not the main objective, just a side effect.