# FW Plenum



## AtRandom (Sep 11, 2010)

Hey guys, not sure if this should be in the planted section instead, but I put it here b/c its a DIY! I randomly stumbled accross some plenum literature (for saltwater) and was wondering if I can apply this to my freshwater refugium system. Last night I was rearranging all my little tanks to accommodate for yet another molly spawn when I thought of this. Now my 10 gallon plants/shrimp are currently sitting in a 5 gallon bucket, while I constructed this thing in about an hour (tank had no substrate in it to start and I already had the other materials and overflow/return setup). I don't want to bother planting it and all that if it's a horrible idea. I'd like some feedback! Below is a diagram I made that close-enough-ly represents what I have.

1. Is it possible to _almost_ eliminate water changes, provided the plenum-fuge is heavily planted and the main tank bio-load isn't ridiculous?

2. Will I still need to use planting substrate? I wonder if I can use significantly less because of all the slow nutrient delivery through the gravels/sands. I will probably have to add iron(Fe) to it, minimally.

3. Will this deplete the water of CO2 from oxygen saturation/water disturbance, or will the aerobic bacteria in the substrate eat up the oxygen?

Some stats: Its a 29 gal down to a 10 gal (less ~3 gallons after modification), moderately-high lighting, DIY CO2 injection into _return_ pump. Main tank is also planted some, but not heavily.
I also have another 29 gal with tetras/port acaras and no plants above which could use this sump instead of using the 29 gallon breeding/planted tank. I have fine-sugar-like sand/kitty-clay/very large sand/small gravel available. Advice towards what I'm neglecting (there's a lot I'm sure) or where this becomes a complete failure is much appreciated!








Okay, I can't figure out how to make my images NOT https from my homepage, here's the link to my project page/picture:
Planted Plenum Refugium - Aquaticopia


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## Big Dog (May 17, 2010)

It looks like it is alot of work Just to use it for your planted aquarium.


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## AtRandom (Sep 11, 2010)

Big Dog said:


> It looks like it is alot of work Just to use it for your planted aquarium.


Well I already have it all plumbed/sealed so the work is done (accept planting the little thing). Setting up the substrate part was pretty quick b/c I had the supplies on hand. My goal is to be able to grow more/healthier/faster plants, without having to buy any more equipment, while simultaneously filtering potentially high bio-loads from the cichlids or else the molly breeding tank. I just don't want to plant it and find out that they are all going to die or something horrible is going to happen. I'm still fairly new at planted tanks, particularly in the nutrient department, as I'm just now getting my hands on "rooted" plants (vs stem/floaters I have collected). My biggest concern is the *substrate* itself. I don't know if I should be using clays or sands and how deep that substrate should be. I may just have to give it a shot, as I need to make a decision soon (my 5 gallon bucket o' plants/fry/snails/ghost shrimp isn't looking too happy - I also accidentally left my 2 most beautiful ghost shrimps in a pint glass over-night, b/c I forgot to re-home them after being distracted, and they died*frown).


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## Big Dog (May 17, 2010)

Once you get into Co2 and Dry fertililzers your plants will take off. I have to cut my plants back at least once a week. That is cool that you where able to get this thing togather. I use Seachem Flourite for my planted aquariums.
I never use sand or clay. I know some people like to use this stuff but what a mess it is if you have to take something out like a large plant or you would like to move some plants around.


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## snail (Aug 6, 2010)

It sounds like a 'beaslbob' build in a sump.
http://www.aquariumforum.com/f15/questions-about-beaslbob-method-8962.html


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## AtRandom (Sep 11, 2010)

snail said:


> It sounds like a 'beaslbob' build in a sump.
> http://www.aquariumforum.com/f15/questions-about-beaslbob-method-8962.html


I just finished planting it, started the pump/syphon, and threw some 20 molly fry in. I will post some pics tomorrow (hopefully). The water is flowing steadily, with maybe 3 "streams" of waterfall down the glass to the return pump. I fed my DIY CO2 hose directly into the intake and hopefully it will diffuse completely as it gets chopped up and travels the hose. Additionally, my ghetto PVC spray bar has a reservoir for any extra gas to be trapped for more diffusion.

I checked out the beaslbob and it actually sounds like...most of my fish tanks! Most (and ALL the larger ones) of my aquariums run filters, however the filters are usually a sponge filter, or a HOB that just has sponge in it. I recently added clover (terrestrial plant?) to the HOB on this 29 gal and its growing like madness. My substrates in most tanks are either all gravel, fine sand, or kitty litter + peat underneath fine sand. I now hate kitty litter. I'm very lazy with water changes, maybe a 15% every 2 or 3 weeks, but I do check the parameters frequently and have low to no levels of ammonia/nitrite/nitrate. I do have uncontrolled amounts of algae, but that's due to overfeeding and lack of CO2, I think. My biggest concern with this concept is the buildup of dissolved organics. I don't know enough about them, but I don't like the idea of plants eating poop, dying, turning into more poop and accumulating (I feed my fish).
With the addition of water (top-off), you will be inevitably adding chemicals (with the exception of RO/DI) to the tank, but not taking them out. Some compounds can evaporate, but I changed my minor away from chemistry because I can't seem to understand much of it! I think the "beaslbob" can and does work, once equilibrium is reached, but it may not actually be the equilibrium desired (example: you can't keep all 5 fish, 2 have to die off before levels are met). I have a 5 gallon Ozarka jug with the neck cut off with about 5 inches of gravel and some random stem plants/mosses floating around. It's called "Hotel Daphnia" and was originally a breeding ground for Daphnia. Now there's 4 mollies in there as well, with what looks like a dangerously high population of Daphnia (I can suck at least 20 of them out with a turkey baster at the substrate without aiming!). I feed them a sprinkle of flakes every few days or weeks (depending on available plants), and have never changed the water (in over 4 months). I have at some times taken plants out for use in other aquariums, during which time I added an air-sponge filter to compensate for lack of oxygen/cleanup. Anyways, I need to sleep! Tomorrow I'm building the 110 gallon stand, finally. I'll post pics of this little "rig" soon! I'll try and get a pick of Hotel Daphnia for ya Snail.


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## snail (Aug 6, 2010)

What kind of algae do you have a problem with? I recommend nerite snails.


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## jrman83 (Jul 9, 2010)

I can't quite picture where your CO2 is feeding, but would be very surprised if you are not bleeding off your CO2 at a faster rate than you can make it due to all the surface disturbance. One way to tell if that is happening is ph testing. Test the ph before CO2 and if it is the same after, then it is bleeding off too fast. Even small amounts of CO2 will cause a ph reduction.


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## AtRandom (Sep 11, 2010)

@ Snail: Its every algae in the rainbow! Kidding, but I have blue/green that is very hard to remove from the glass once it cakes on (which is a PITA with the acrylic tank - which I ruined by scraping wrong finally) and a more dubious hair-like (short though) almost black/grey colored strain that grows on every leaf of every plant as well as my driftwood. I'll try and get me some of those fancy nerites next time I'm at the shop, thanks for the tip!
-On a side-note: 2 of my "Golden Mystery" snails, originally housed in the sump, climbed up the 5 gallon bucket last night and laid a nice huge egg bunch! I wonder how I need to "incubate" them (trap humidity? Not underwater I assume). They were laid a good 6 or so inches above the water line.

@Jrman83: Thanks for the tip, good call! The CO2 hose sits right at the inlet to the return pump, where you can see the bubbles being continuously sucked into the motor. Once sucked into the motor some get's "backfired" (through another hole in the pump, as the pump was taken out of a discontinued-discounted HOB filter I got for $6) while the rest goes flying through about 4 or 5 feet of clear flexible hosing. I can see the micro-bubbles enter the hose, but none towards the end (in the main tank), which leads me to believe the bubbles that do travel the hose are completely diffused. There is almost 0 surface disturbance in both tanks, apart from the small HOB, leaving the short drop into the sump as well as the short waterfall as the main places of gas exchange. I hypothesize that the plenum substrate will become rich in aerobic bacteria, which will eat up oxygen entering it, while the main tank will be supplied with CO2 to compensate for off-gassing that occurs from the trickling "waterfall" into the return chamber. I'll have to test the pH with/without CO2 when I get a minute!


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## beaslbob (May 29, 2009)

Plenums were popular for marine tanks a decade or so ago.

see: Jaubert Live Sand Filtration

the jaubert system used a deap sand bed (dsb) with plenum and a skimmer. the idea was to grow anoxic/anaerobic bacteria in the plenum/dsb to reduce nitrates. also referred to NNR (natural nitrate reduction).

In the last few years some have done tests and discovered that there is no additional nitrate reduction with or without the plenum.

Additionally, some have experienced "crashes" in the DSB operation especially after ~5 years or more of operation. My speculation is the DSB when working reduces nitrates but does nothing for phosphates. So at the sand's surface you have a low oxygen, high(er) carbon dioxide, and phosphate environment. Plus the bacterial action reduces nitrates to nitrogen gas. Cyano can fix that nitrogen gas for its nitrogen so the environment is almost exactly what cyano needs to bloom. Robbing more phosphate from the corals and algae in the system. So the tank can rapidily become cyano dominated.

When the DSB is not working correctly it can actually return ammonia to the system and dangerous sulfide compounds as well.

In the last few years, IMHO there has been a return to refugiums with algaes which results in a more balanced nutrient uptake and stable operation.


One of the reasons for all that in marine systems is the total lack of easy to grow fast growing true plants in marine systems. Unlike our Fw systems.

Although many ideas from the marine systems especially refugiums and live rock, do have great use in Fw setups, the plenum would seem to be useless.

At least to my way of thinking.

(which has been wrong before.)


(once)

my .02


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## snail (Aug 6, 2010)

My nerites love all the blue green, diatom type algae, I actually am leaving the tank lights on for about 13 hrs a day to grow more algae!! It's cool to see them eating off the plant leaves. My anubias has never been cleaner! They don't touch the tougher algae like Cladophora though, so I'm not sure about your hairy algae.

Algae problems are often due to too much light or dirty water too.


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## AtRandom (Sep 11, 2010)

I haven't been on the forums in ages, but forgot to give a followup on this. It did grow the plants and the fish and shrimp were merry. Using the reverse-gravel filter style for the sump may or may not have been superior to normal sumping - but there were a few things to note:
1. There should not be plants in both sides, otherwise I should just be using 1 larger aquarium.
2. The sump substrate got very full of particulate after a few months and any disturbance caused quite a cloud.

I only ran it for a couple of months before I moved all the plants over to my 110 after it was set up. I just recently found a huge video segment I had made a very long time ago for this thread showing all my little wierd aquarium experiments. I chopped it up and tried to make a brief explanation of the "plenum" refugium/sump we discussed here (and it turned out not really being a plenum at all really, more of a reverse undergravel sump):
YouTube - Experimental Planted Freshwater Sump

@Snail - not sure if you're still around, but I've got some nerites rocking my larger tank now, but they are still very young and I hardly ever see them (they are accompanied by a BN pleco pair and a half dozen ottos).


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