Someone asked me how a Reverse Undergravel Filter works and what is the advantage.

[Paul B]

@Paul B can an RUGF be effectively used with a moderately deep 2-3" sugar sand bed? I already got the sand with wrasses and gobies in mind.

No, as was said, sand will not work for long at all

I guess one reason I'm questioning this is because Paul has a picture of his plates being lifted up out of the tank covered in "mud".

Mud will accumulate in anything after 30 years. If you stood still for 30 years, mud would accumulate under you.

Remember if you have an established reef and not one that people take down every 15 minutes to catch fish to put in quarantine, the corals and rock will be kind of cemented together so it is very hard to move and you can't physically get under there to stir it up.

That mud in my old tank was mostly under the rock. I think I lifted the UG filter plates then to re aquascape because I built a lot of new, large hollow rock out of cement and I gradually came up with the theory that a reef should be a lace like structure so water can flow everywhere and now my tank is like that.

The tunnels go from one end of my 6' tank to the other. It is entirely caves and holes which is why I can have fish in there for a year and never see them.

WE may not like that but the fish love it. This is a huge problem in all these tanks with disease. Most people can't read the expression on a fishes face and fish in non natural looking tanks have an expression like Nancy Pelosi. Think deer in headlights. ;Wideyed

Fish that feel safe and are fed correctly never get sick.

It's like if we were abducted by Aliens (from space not South America) and they were really ugly looking beings and they kept us in a place that was built out of old Milli Vanilli CDs (Google them)

 

[KrisReef]

Mud will accumulate in anything after 30 years. If you stood still for 30 years, mud would accumulate under you.

Oh, I wondered what that was. Thanks Paul!
The career of a dedicated state worker has me accumulating a huge pile that has made me very unpopular lately.

 

[pseudorand]

What about nitrates?

RFUG and canisters are supposedly nitrate factories. I have a 120 with a partial RFUG (I couldn't find plates the right size) and a canister simply because I used to to freshwater and didn't know any better. After 2 years, I have 44 species of coral that haven't died yet, many of which are staring to take off. This includes 4 species of acros and two sylos as of this weekend (local reef club guy needed to cut and sold them cheap).

However, true to the stories, my nitrate and phosphates are persistently high. NO3 @ 10ppm and PO4 @ .1 ppm. I use phosguard and do bi-weekly 10%s, and I have a skimmer and fuge with cheato. I dose and have and ATO for stability too.

I give my new acros a 50/50 chance, but they were destined for calcium reactor media if I didn't buy them, so I don't feel too bad.

What about other with RFUG? What are your nitrates and phosphates? Does anyone with levels that high successfully keep sticks?

 

[Jekyl]

What about nitrates?

RFUG and canisters are supposedly nitrate factories. I have a 120 with a partial RFUG (I couldn't find plates the right size) and a canister simply because I used to to freshwater and didn't know any better. After 2 years, I have 44 species of coral that haven't died yet, many of which are staring to take off. This includes 4 species of acros and two sylos as of this weekend (local reef club guy needed to cut and sold them cheap).

However, true to the stories, my nitrate and phosphates are persistently high. NO3 @ 10ppm and PO4 @ .1 ppm. I use phosguard and do bi-weekly 10%s, and I have a skimmer and fuge with cheato. I dose and have and ATO for stability too.

I give my new acros a 50/50 chance, but they were destined for calcium reactor media if I didn't buy them, so I don't feel too bad.

What about other with RFUG? What are your nitrates and phosphates? Does anyone with levels that high successfully keep sticks?

I wouldn't consider those numbers high

 

[Lasse]

I do no WC and run my tank with RUGF (more like a remote reversed DSB) - my PO4 are around 0.1 and NO3 vary between 1 - 5

Sincerely Lasse

 

[Paul B]

I have no idea what my PO4, No3, HDTV or H2O readings are.

 

[Builderguy]

I'm still trying to wrap my head on why the reverse flow is important. Is it just because detritus is pushed out of the media/substrate rather than sucked in?

Is prefiltering important?

As all things that work perfectly, I want to try something different. I'm looking at using a square bucket a 40 breeder to hold substrate for mangroves and I would like to keep it aerobic if possible. So I'm exploring the design, I'm kind of at a radial side draft idea right now.

 

[Paul B]

Builderguy, I don't know either. I do know we all started with fresh water and we all had undergravel filters. (I am talking in the olden days of course)

When salt came out we kept the UG filters and put in salt water. After less than a year it was a disaster. The thing clogged and was totally filled with detritus and it turned into black hydrogen sulfide pushing many people out of the hobby.

As for your mangroves. I also keep them but they need no substrate. Just coral rock to keep them upright.

Thats how they grow in mangrove forests. That sand is not needed

 

[SmCaudata]

I'm going to setup a somewhat large tank (~200g) I'm intrigued by this thread. I know that you set up yours a long time ago, but if you were doing a new tank now, would you do the an undergravel in reverse? Do you still run a sump for convenience of a skimmer, heater locations, dosing, carbon, etc?

 

[Jekyl]

I'm going to setup a somewhat large tank (~200g) I'm intrigued by this thread. I know that you set up yours a long time ago, but if you were doing a new tank now, would you do the an undergravel in reverse? Do you still run a sump for convenience of a skimmer, heater locations, dosing, carbon, etc?

I run an RUGF system, no sump. HoB filter and HoB skimmer.

 

[SmCaudata]

I run an RUGF system, no sump. HoB filter and HoB skimmer.

I guess. Is there a reason to not run a sump? I was wondering if I could plumb a return pump to go down the UGF tubes with anti-backflow or anti-syphon. Maybe I'm just asking for disaster if those parts were to fail...

My planned dimensions are 72x30. Would a 72x18 filter like the lee's premium work? or do I need more coverage on the bottom to prevent stagnant areas?

 

[Jekyl]

If I wer

I guess. Is there a reason to not run a sump? I was wondering if I could plumb a return pump to go down the UGF tubes with anti-backflow or anti-syphon. Maybe I'm just asking for disaster if those parts were to fail...

My planned dimensions are 72x30. Would a 72x18 filter like the lee's premium work? or do I need more coverage on the bottom to prevent stagnant areas?

You can run a sump. I probably would if done again. However the RUGF system needs to be independent of this. You need low flow going back into the plates. I have a 90g with 2 separate plates and a 250gph pump feeding both.

 

[SmCaudata]

If I wer
You can run a sump. I probably would if done again. However the RUGF system needs to be independent of this. You need low flow going back into the plates. I have a 90g with 2 separate plates and a 250gph pump feeding both.

I was thinking of a controllable DC pump so that I could keep the flow low, but the more I think about it, the less keen I am depending on some mechanical valves being all that stands in the way of a tank being drained to the ground. Closed loop or low flow power heads probably makes a lot more sense from a safety standpoint.

So, as to size, could I get by with only 18" of coverage on the 30" front to back depth? or do I need to build something custom? 18" is the widest I can find.

 

[Jekyl]

I was thinking of a controllable DC pump so that I could keep the flow low, but the more I think about it, the less keen I am depending on some mechanical valves being all that stands in the way of a tank being drained to the ground. Closed loop or low flow power heads probably makes a lot more sense from a safety standpoint.

So, as to size, could I get by with only 18" of coverage on the 30" front to back depth? or do I need to build something custom? 18" is the widest I can find.

The 18s would still serve their purpose I believe. You don't want a closed loop system where water is being sucked out of the plates. You want water being pushed in and coming up through the substrate.

 

[SmCaudata]

The 18s would still serve their purpose I believe. You don't want a closed loop system where water is being sucked out of the plates. You want water being pushed in and coming up through the substrate.

Last question for now: is there a reason you went with two vs one?

 

[Jekyl]

Last question for now: is there a reason you went with two vs one?

The plates don't come in 48" wide. So I installed 2 that were roughly 18x24 each and plumbed them together.

 

[Paul B]

but if you were doing a new tank now, would you do the an undergravel in reverse? Do you still run a sump for convenience of a skimmer, heater locations, dosing, carbon, etc?

Remember I relocated my tank to my new house here 4 years ago and installed the RUGF exactly the same way with the existing gravel which I rinsed a little in sea water to remove years of mud.

UGs in salt water must be run in reverse. We all tried it the normal way when salt came out and it was a disaster for some reason.

I don't use carbon because I feel it eliminates to many good things and any bad things are eliminated more naturally with my algae scrubber.

I don't have a sump because they were not invented when I started my tank. Not that I have anything against them. My tank is filled to the top so you don't see any heaters.

 

[Duncan62]

Someone asked me how a reverse Undergravel filter works and what is the advantage of it.
In the beginning, when we all kept bait, I mean fresh water fish we all ran undergravel filters. That was the only way to go and in fresh water they work perfectly.

When salt water started for home tanks in 1971 in the US (a little before that in Europe) some of us switched our tanks to salt but we kept our UG filters. Most of us did change the gravel to something different than the purple broken glass we had in fresh water and we removed the sunken chests and deep sea divers fighting sharks but there was no salt water gravel available.

After unsuccessfully using blue driveway gravel I discovered dolomite. You can still get it at a mausoleum or museum, maybe an archaeological dig in Egypt, I don't know but I assume crushed coral would also work.

I first ran my salt tank using a normal UG filter and in less than a year it crashed and I had to rescue my fish. There was no coral, live or dead rock then but we did have bricks, cinder blocks and roller skates. Much of my "rock" was asphalt that was dumped in the sea before I was born. I still have some of it and if you look close you can probably see remnants of the yellow line that was painted on it when it was a street.

I am not sure what the problem was by using a UG filter the normal way. We didn't have powerheads so they were all run with bubbles and they didn't run to fast but the salt creep on the lights caused us to have to turn on the lights with a stick because GFCIs were also not invented. As a matter of fact, to do anything on the tank we had to unplug everything and the only thing we could keep with success was electric eels.

Anyway, the UG filters, after a few months became totally clogged rendering them useless similar to some politicians.

I decided to reverse the thing and instead of the water going down through the gravel, now it came up through the gravel. Something happened. It was a good thing. The tank didn't crash. It kept going and fifty years later it is still running.

Not crashing is a good thing but not the only benefit. I learned from Robert Straughn "The Father of Salt Water Fish Keeping" that the bottom of the tank is the perfect filter and the largest thing in the tank. Mr. Straughn used UG filters constantly but at that time, in the 50s he didn't quite understand the function of bacteria like we do today and he used the filter as a particle filter.

That works but you have to clean it constantly and as a whole, humans are lazy.
I discovered that if you pump water through the gravel at a slow speed and maybe strain it of particles first, the thing would not only last forever, 50 years anyway, but the tank would thrive and it would be easier to keep smaller fish.

A sand bottom has very little oxygen going through it as it is stagnant. But gravel, even if it is just sitting there has water flowing all through it. But if we give it a little help and push a little water through it, multitudes of creatures colonize it causing it to be a huge eco system.

Tiny tube worms, brittle stars, pods and bacteria completely fill every void. Those tube worms filter the water and the brittle stars remove particles. Very little detritus is left and a little detritus is good because it even provides more living space for those creatures which hate clean, sterile places to live sort of like Ozzie Osborn.

Those tiny creatures can breed in multitudes feeding smaller fish like pipefish, mandarins, dragonettes and anything that eats pods. I have many of those fish, they are all spawning and I never have to feed them.

This silly thing is the manifold I used for many years. I built a new one now but it is the same principal.
It is of course an old HOB filter. The three tubes coming out the bottom go to each of the 3 UG filter tubes.

The one on the left doesn't do anything and was a mistake, it is blocked.

Water is pumped into the thing from that hose on the left. I don't have a sump or I would have to divert some water from that to here.

I run about 250 GPH down each tube so about 500 GPH is pumped into the manifold where the water is evenly separated. Faster flow is no good, it has to be slow.

Once or twice a year I stir up the gravel where I can reach with a canister filter or diatom to remove excess detritus. If it was left forever it would probably clog eventually and besides, I like doing it.

Of course if your present system lasted longer than fifty years, do that. ;Joyful

I remember when these were new technology.

 

[Paul B]

I do too.
I also think I may have been the first one to run them in reverse. But I am guessing because with no internet, no one knew what anyone else was doing.

 

[snorklr]

think we had to read about them in Tropical Fish Hobbyist....