How does an undergravel filter work???

[daveedka]

Don't you just hate repeating yourself so often?

Some days I do, but then again if one more person learns something valuable then It's a payback for everything others have helped me learn.

I did many UG/RFUG filters for years, then largely got away from them for a period, but my numbers are going up again (all OE-RFUG), and my tanks are looking (and test) great.

With the planted RFUG's I am trying very hard to find a downside. Thus far I cannot find one. The more I study it the more I dount I will ever get away from the RFUG set-ups. My next tank will be RFUG with Flourite, I know rinsing will be a PITA, but with my tap water I think it will be worth the trouble to start out enriched. I am currently running a plastic tub without RFUG where I do my plant grow out and also have some guppies and snails going strong. I can't really see any reason thet the flourite wouldn't work on the RFUG, but time and experimentation will be needed.
Dave

 

[RTR]

I have a 50:50 mix of Flourite and conventional gravel planted over OE-RFUG. It was recycled from another planted tank (one of the old plenums) so rinsing was no worse than ordinary used gravel would be. But I do have a rather elaborate gravel wash setup for temperate-weather use. I do need to write that up, but many folks would be rolling on the floor. My feeling are that he who laughs last...

 

[toofazt]

1. How do I hook the ugf up so it will be reverse flow undergravel?
2. If I do a rfug then do I ever really need to clean it out at all?
3. How much gravel do should I lay over the rfug filter?
4. If I put my hand on the gravel will I be able to feel water pushing out of the gravel; wouldn't that bother the bottom dwelling fish?
5. Do you find that it evenly spreads out the water flow coming through the gravel, or are some areas of the gravel cleaner than others?
6. I'm assuming that you do a rfug filter useing 2 power heads. What size power heads would I need for a 60gal, a 120gal?

!THANKS!​

 

[daveedka]

1. How do I hook the ugf up so it will be reverse flow undergravel?

The easiest and IMO the best way is to use penguin powewrheads penguin makes a ready made filter kit for reverse flow, and the powerhead is made to turn around rather than switch motor direction. other systems switch motor direction and that is not as effecient.

2. If I do a rfug then do I ever really need to clean it out at all?

Water changes are still necessary, and light vcaccuming if you don't like the look of mulm laying on top of your substrate. I have two tanks that get no vaccuming whatsoever, and there is usually a light dusting of mulm visible on the gravel.

3. How much gravel do should I lay over the rfug filter?

1" minimum, if you plan to plant you can go as deep as 3"

4. If I put my hand on the gravel will I be able to feel water pushing out of the gravel; wouldn't that bother the bottom dwelling fish?

Nope, there is very little noticable or "felt" current created by a UGF or RFUG set up despite the large water turnover rate.

5. Do you find that it evenly spreads out the water flow coming through the gravel, or are some areas of the gravel cleaner than others?

For the most part the flow is even, decor and plant roots will slow it in some areas, but there is still flow through all parts of the substrate as far as my experiments indicate.

6. I'm assuming that you do a rfug filter useing 2 power heads. What size power heads would I need for a 60gal, a 120gal?

I personally run a bit more flow than most Foks do. For a 60g I would run two penguin 1140's, most folks would probably run two penguin 660's. For a 120g I would run 4-6 1140's depending on tank dimensions. my 115g is a 48"x18" tank and has 4 1140's running on it. Higher flow definately runs better IMO and IME but low flow works well enough. The more motors you submerge in a tank, the more heat is created. at some point you have too much heat and you run into warmer water than you may want to have. additionally if you run other internal filters as RTR often does you have less margin for bigger powerheads. In my case, I run mostly HOB's which don't have the side effect of adding heat. Right now MY 115 runs 4 1140 pengiuns on the RFUG, 1 550 pengiun on the co2 reactor, and two additional powerheads (I forget model and size) for current. it also has an eheim aquaball filter running in the tank, and I have yet to see heat issues. In smaller tanks the heat becomes more of a side effect with high flow. I haven't yet put together watts of motor per gallon type specs to give you any real guidelines on where the limits might be.
dave

 

[zazz]

Too little information too late I am sure, but next time insert a 1/4" (or bigger if it fits) airline through the riser tube hole and then vaccum under the plates with that. once the majority of the gunk is out, you can influence flow by making thin spots in the substrate (temporarily of course) this will move the mulm around and allow it to flush out.

Thank you! Not entirely too late as I am starting a new tank with ugf.

In all respects except up front price the Reverse flow set-ups are superior. With my planted tanks, vaccuming isn't a good practice, so reverse flow is a must. Aditionally reverse flow provides a good bit of true mechanical filtration via-the intake sponges on the pwerheads.

Just an FYI, while the mulm does not collect in the substrate with reverse flow like it does in conventional, the munute particles in the water that do get through the prefilters are still caught in the substrate so the end result is much cleaner substrate but you still get the ultra polished look that many people want in their tanks. Hands down nothing polishes water any better than a UGF or an RFUG. Only diatom filters or micron filters compare and they are of course harder to maintain and more expensive.
Dave

Two things that I hadn't realized. Obviously I have only read about, not used a reverse flow under gravel. Sorry if I was misleading in earlier post.
Your answers to toofazts enumerated questions were helpful to me as well.

 

[FishSeller]

With RUGF in a planted tank, you also eliminate the need for substrate cable heaters as heated water is being physically pumped through the gravel. I've never used one personally, but I definately see the advantages of this set-up. With RUGF, are "dead spots" in the filter still an issue the way they are in a regular UGF?

 

[RTR]

I am one of the folks with over-heating problems. I massively over-filter all of my tanks, and my house/ambient temps are very stable and tightly controlled. I have not needed heaters since we built this place, but the other side of the same coin is that my tanks run a bit warmer than I would like. The last planted RFUG I set has two Penguin 1140 powerheads driving a 29 gallon RFUG, plus two old Fluval 2 (not the "improved" 2a) internal canisters for extra mechanical and current. The tank ran over 82F all the time, so I set a small fan under the tank (one of my few stands with a viewable tank base) which dropped the tank temp a couple of degrees.

I'd like to reset the 55 in the same room planted RFUG, but I know it would be worse, as its internals are Eheims, a bit larger and a bit more wattage than the old Fluvals, plus it has a bit higher lighting/gallon (more heat input). I hate going to Eheim external canisters for the extra mechanical, as they are not as user friendly (easy) to rinse on a weekly basis. I'm still waffling on that one.

 

[janderson]

excuse the newbie question, but

in order to convert from UG to RFUG, is a reverse-flow capable powerheads (like the Penguin 660R) all you need or are there any other parts necessary ?

Thanks.

 

[daveedka]

In the case of the 660 R it is the 660 powerhead complete with the reverse flow sponge kit, so it is all you would need.
If buying other models of penguin powerheads, or if you already own a 660 then you simply need to purchase the reverse flow sponge kit. The kit comes with everything you need to set up any penguin powerhead in reverse flow configuration.

There are some other brands that have reversable powerheads, rather than making it easy to actually turn the powerhead around. Reversable pumps are never as good backwards as they are forward so these lack some appeal IMO.

With any reverse flow set-up the real key is to make sure there is a filter of some kind to prevent the mulm from getting pumped under the plates in high volume. This can be a DIY project or you can go with ready made parts like the penguin kit. To me the penguins are extremely economical and dependable for the money, and the ready made reverse flow sponge kit is simple and inexpensive.
Dave

 

[Joele]

Thanks daveedka for defending the UGF LOL, I was horrified reading some of the earlier posts slamming it but obviously due to a misunderstanding of how it works...

I am new to this forum although not new to aquaria (although I have been in marine for the last 5 years) recently getting back into freshwater, and went with an UGF... I always preferred undergravel to those HOF, I had tried them on various tanks but always prefered the UGF.

I don't use Reverse Flow I use a standard UGF and had one running for 4 years before I had to break the tank down (due to moving house) and it wasn't clogged up at all, although my nana had a healthy root system under there... It is far from true to say you need to pull your tank apart each year... A 4 weekly gravel vacumn was my UGF maintanence technique... Although one thing I would point out I would tended to give a good vacumn of just one side of the tank each 4 week cycle (alternating each time)...