Freshwater Sump / Refugium

[thiswasgone]

I'll admit... this is getting a bit over my head. But I'm doing my best to keep up.

After a few google searches, do you agree that in laymen's terms heterotrophic bacteria/archaea is the bacteria that feasts on solid waste breaking it down into smaller parts more readily available to be processed by NH3-to-NO2 bacterial process we all know and love.

If so, isn't this bacteria mostly grown on the waste itself? It seems to me this bacteria will thrive in the mechanical chamber and will be a bit out of place in a chamber in the sump that does not target the collection of physical waste. And we wouldn't need to provide high surface area media, as it grows in, on, around the waste itself.

I also read: " Heterotrophic bacteria can reproduce very quickly, sometimes doubling in population every 20 minutes."

This misunderstanding seems to come from aquarist believing in a hard separation of mechanical and biological filtration. Fundamentally all mechanical filter media can act as biological filter media as beneficial bacteria (both heterotrophic & autotrophic) simply require water flow + surface area to attach onto and grow. Additionally, bacteria typically do not grow into standalone colonies, most micro-lifeforms have various co-existance relationships and in this case both will live in the same colony. We do not use mechanical and biological filter media interchangably because mechanical media either has enough surface area but is not porous enough to allow water to flow through or the reverse -> bacteria colonies either further clog up the filter or not enough surface area to grow effective colonies -> tank won't cycle properly. Thus, mechanical media is usually reserved for "polishing" the water quality by removing visible solids but not necessarily biological filtration.

This is why the best biological filter set ups use sand, beads, or kaldness media; they maximize surface area while also allowing for water to flow through/around them for tumbling or even in static formations. Thus, most of the heterotrophic bacteria will still be on your biological media ergo why "overfiltration" is a little bit of a myth but there definitely needs to be some cost-benefit analysis done to check if it is worth it compared to just more water changes.

 

[triamond]

So the 4ppm (daily) turned into 3 ppm, not 5

Yes… I thought about net water (total ‘external’ volume minus glass/acrylic, sand, free space at the top, rocks, wood, background, etc.)… it could be 75%. Similar for the sump, minus space for overflow/media/baffles/pump/sand, etc. – 50%.
3,785 * (195 × 0.75 + 75 × 0.5) = 695 (l) and about 4.3 ppm of NO3 daily (5.4 ppm for the aquarium only).

I think 60-65 ppm of nitrates per week for a single Oscar being properly fed in a 75 gal with no plants is high.
Not ridiculously high. But high. I'd expect 30-40.

Sounds reasonable
Complicating things...
Some of the nitrates (quantitatively) will be used for building bacterial mass.
Some will be held in not-so-labile organic substances that are not prone to mineralization (refractory DOC).
Tests will detect only the mineral final product of the process.
Some will be consumed by plants, fish growth, and algae.
Some will be removed during cleaning of mechanical media if present (but not much, as 85% of N is removed through gills in soluble form (NH3)).
The system (heterotrophs) is carbon (energy) limited, as fish produce energy from the oxidation of proteins, fats, and some carbs. Undigested ingredients are a source of energy. Rotting wood could be a source of carbon, so biofloc building should remove more nitrates.

But... will dedicating 40ish gallons of my sump to a refugium offset the waste to a degree that makes it worth having?

For educational purposes only If aquaponics is planned… no! Algae scrubbers, no!
Plants can use 10 times more light than algae; there is 1000 times more CO2 in the air. Aerial plants can grow 4.5 times faster than water plants, and water plants can grow 2 times faster than algae. There is much more water in algae than in aerial plants…

I also read: " Heterotrophic bacteria can reproduce very quickly, sometimes doubling in population every 20 minutes."

In water, it's easy to cause a bloom. But it takes time to build a proper life in the filter to starve out free-floating bacteria or feed on them. Enough space, flow, and oxygen are required.

s the bacteria that feasts on solid waste breaking it down into smaller parts

This is just a start – to break it into soluble components… then soluble organics need to be oxidized to CO2.
...
You don't need sand… just put a Pothos stem into water anywhere, and water roots will appear.
Sand will reduce the durability of the pump and will soon clog… bad idea.
I agree with @duanes and @jjohnwm on baffles (in terms of space), pump compartment, and overflow/dry run risk.
Things are even more complicated with a constant water changing system, as water goes down the drain when the pump stops (if it's on the pump side) or when it starts (on the sump input; not tested).
On the other hand, baffles increase speed through the filtration medium, which can be beneficial if there is not enough flow to cause turbulent movement close to the medium surface… No problem in MBBR.

 

[Toby_H]

Sigh... You're not telling me any of what I want to hear.

So, if I understand you correct...

You have explained that, based on your numbers, a 40-50 gallon chamber of a sump on this 195 gallon tank / 270 gallon system will not be able to host enough plants to do a worthwhile job at cutting nitrates & other bio-waste. Acknowledging it will offer some benefit, but not enough to justify it's space, energy, time to maintain.
I've still not accepted this, but you have my attention well enough to consider other options...

In your first post here, you suggested 30PPI Media or MBBR Kaldness.
As you (and others) have suggested against making multiple baffles / chambers, I don't understand the function of a huge chamber loaded with foam. It makes more sense to me to funnel water into a narrower space such as a 3.5 x 18 space between baffles and place this foam there. And I already have a couple such chambers designed in. Note: I'm becoming less and less convinced of my "Sand Bed" as filter media and will likely abandon it for something such as 30ppi.
I've seen MBBR media mentioned elsewhere (in a Discus filtration article) but I'm not personally familiar or well read. Having now glanced at a few articles, it seems like nothing more than more efficient Bio-Media to host the common bacteria that transforms Ammonia to Nitrate. And since we've already established this system, like most systems, will have ample "surface area" for sufficient colonies of bacteria to perform this function.

So... If I only need a small chamber or two for 30ppi, and Bio-Media to host Ammonia to Nitrate bacteria adds nothing... what should go in this chamber if not plants? Previously you suggested adding tons of 30PPI Media or MBBR Kaldness but I just don't see the effectiveness in that. I'm not saying you're wrong, but asking you to help me see what I'm missing.

 

[Toby_H]

This misunderstanding seems to come from aquarist believing in a hard separation of mechanical and biological filtration. Fundamentally all mechanical filter media can act as biological filter media as beneficial bacteria (both heterotrophic & autotrophic) simply require water flow + surface area to attach onto and grow. Additionally, bacteria typically do not grow into standalone colonies, most micro-lifeforms have various co-existance relationships and in this case both will live in the same colony. We do not use mechanical and biological filter media interchangably because mechanical media either has enough surface area but is not porous enough to allow water to flow through or the reverse -> bacteria colonies either further clog up the filter or not enough surface area to grow effective colonies -> tank won't cycle properly. Thus, mechanical media is usually reserved for "polishing" the water quality by removing visible solids but not necessarily biological filtration.

This is why the best biological filter set ups use sand, beads, or kaldness media; they maximize surface area while also allowing for water to flow through/around them for tumbling or even in static formations. Thus, most of the heterotrophic bacteria will still be on your biological media ergo why "overfiltration" is a little bit of a myth but there definitely needs to be some cost-benefit analysis done to check if it is worth it compared to just more water changes.

I do understand and agree with your point about Mechanical nor Bio-Filtration being standalone processes.
I've argued for 20 years that most Bio-Media is hype because the bacteria will form on all available surfaces and its exceptionally rare for any aquarium system to not have enough available surfaces to host an appropriate sized bacteria colony. I've adapted to using the terminology but rarely put any time, effort or money into adding "Bio-Media".

Therefore, a system without "Bio-Media" that has appropriate "Mechanical filtration" will simply have a mechanical filtration chamber loaded with beneficial bacteria. And likewise, a system loaded with Bio-Media will still have a mechanical filtration chamber loaded with beneficial bacteria. Just like the sand, rocks, pipes, etc, etc are coated with beneficial bacteria.

This is why I'm struggling to wrap my head around the suggestion of adding bio-media instead of a refugium. I accept the sized refugium I'm working with will not remove the need/benefit of water changes, but it will reduce the nitrate/phosphate/other build up. My goal is not to remove the need for water changes, it is to reduce the waste build up between regular weekly water changes.

It's also worth noting that a "Mechanical Filtration" system will be added in addition to the sump. The 2 main reasons I'm adding the sump is to increase overall water volume (the solution to pollution is dilution, as is said in environmental engineering) & to offer dedicated space for plants to eat away at waste byproducts. And you guys are breaking my little heart by explaining how my whole second reason isn't nearly as reasonable as I thought.

 

[thiswasgone]

I do understand and agree with your point about Mechanical nor Bio-Filtration being standalone processes.
I've argued for 20 years that most Bio-Media is hype because the bacteria will form on all available surfaces and its exceptionally rare for any aquarium system to not have enough available surfaces to host an appropriate sized bacteria colony. I've adapted to using the terminology but rarely put any time, effort or money into adding "Bio-Media".

Therefore, a system without "Bio-Media" that has appropriate "Mechanical filtration" will simply have a mechanical filtration chamber loaded with beneficial bacteria. And likewise, a system loaded with Bio-Media will still have a mechanical filtration chamber loaded with beneficial bacteria. Just like the sand, rocks, pipes, etc, etc are coated with beneficial bacteria.

This is why I'm struggling to wrap my head around the suggestion of adding bio-media instead of a refugium. I accept the sized refugium I'm working with will not remove the need/benefit of water changes, but it will reduce the nitrate/phosphate/other build up. My goal is not to remove the need for water changes, it is to reduce the waste build up between regular weekly water changes.

It's also worth noting that a "Mechanical Filtration" system will be added in addition to the sump. The 2 main reasons I'm adding the sump is to increase overall water volume (the solution to pollution is dilution, as is said in environmental engineering) & to offer dedicated space for plants to eat away at waste byproducts. And you guys are breaking my little heart by explaining how my whole second reason isn't nearly as reasonable as I thought.

I wasn't 100% clear, let me clarify. My previous post was created to address your statement that the bacteria would grow primarily on the waste; this is not entirely correct. As you properly summarized, beneficial bacteria will grow on almost any surface and that most heterotrophic bacteria species will "reproduce" extremely fast (some doubling their population in 15mins in ideal conditions) however, as addressed in my post, it would appear you misunderstood what exactly is beneficial bacteria in the home aquarium and how it thrives. "Beneficial bacteria" is typically used as a general term to describe autotrophic nitrifying bacteria however in reality it is actually describing a complex mixture of heterotrophic and autotrophic bacteria colonies which coexist within a biofilm they produce to anchor themselves in areas where their food is present. Additionally, the biofilm becomes a host for various other micro-organisms such as water molds, fungi, etc.; in short, it is a mini-ecosystem within your filter.

The biofilm itself will grow and expand over time covering the entire surface of the media but it won't be impermeable to water; at least on the micro-level, biofilm can clog up your media/filter/returns. To imagine the structure of biofilm you can think about how living bone marrow looks like or the honey combs within a beehive; there are various micro openings/caves that extend throughout the structure. While this allows for "food" to reach all throughout the biofilm unfortunately this very structure causes an interesting natural selection to occur. Almost all autotrophic nitrifying bacteria will live on the outer most parts of the biofilm because the structure encourages a first-come-first-serve bias. Since the nitrifying bacteria we want are not free-floating they have to wait for "food" to come to them within the biofilm = water flow brings them food -> nitrifying bacteria on the outer edge of the biofilm get fed first while those inside either starve or die off. This is because the chemcial reaction to oxidize ammonia into nitrate (nitrification) is a very low energy reaction so these bacteria require enourmous amounts of ammonia & nitrite molecules to survive. Of course this doesn't mean the internal parts of the biofilm can't house nitrifying bacteria but 99.9% will live on the outer edges of the biofilm.

This is why Moving Bed Biofilm Reactor (MBBR) or Moving Bed Reactor (MBR) are the most efficient nitrifying biological filteration we have at the moment. Most of the volume within a biofilm is taken up by either heterotrophic bacteria or other micro lifeforms that aren't contributing directly to nitrification (remember, they do start the process though by breaking down solids into ammonia so they are still important). Thus, when you cause the media to "crash" into each other and encourage your beneficial bacteria to maximize it's usage of surface area but minize it's volume you get the most autotrophic nitrifying bacteria per given volume. Herein lies the eternal problem for the home aquarist. It's a game between how much space can I allocate for my fish and how much space must I allocate for optimal beneficial bacteria growth. Of course in theory it's completely possible to run 0 external filters and keep your fish in a single planted tank but the overall bioload has to be relatively miniscule; this is how so terrariums can exist for many years without being a biological deadzone.

edit: However, if you don't want a MBBR (it's too loud, too expensive, etc.) it's completely fine to run other methods. The key thing, as mentioned in my last post, is simply flow + surface area. If you concentrate both in one spot you effectively can make almost any surface your biological filter.

Of course you care more about how to remove the nitrates in your system rather than me explain and math out an optimal MBBR so i'll be brief regarding the main topic of the post. In short, it's not feasible for a 90g by itself to contain enough plant mass. @triamond 's calculations look on point with my own understanding, readings, and attempts and it's simply not possible for aquatic only plants. @duanes system is the best solution i've seen actually implanted on any forum short of SE Asia's industrial scale freshwater fish-farming methods (many use entire pools as their filter with a lot of terrestial plants). However, even those farmers have to bring in fresh water eventually. My final suggestion is to look into how aquaponic systems are setup if you still want to continue down this path otherwise you'll have to go get a pool to make a planted tank worth it for an aquatic only solution.

HTH

 

[Toby_H]

Gotcha...

Triamond said, " However, the filter is also supposed to degrade uneaten and undigested food and feces into CO2, NH3, etc. This is the role of heterotrophic bacteria/archaea. Much more space is required (20-100 times), as this process is more complex."

That didn't make sense to me. Specifically, the bacteria that breaks down the physical waste, would exist on the physical waste, wouldn't it? I don't understand how bacteria on the front glass, or on a rock in the aquarium, will break down physical waste that got picked up in the filter. That said, I do understand that once the physical waste is broken down into it's chemical components, the bacteria on the glass or a rock will consume those chemical compounds, as they are then in the water column.

You gave a beautiful description of how most bacterial colonies exist and evolve in our aquariums.

_____________________________________

This thread has gotten fairly complex, and I thank all of you who contributed to that.

I have decided to abandon the the sand as filter media... It's a choke point in the sump and I don't have a plan of how to clean the sand. It seems much more practical to stage sponges in that chamber. I'll likely get several grades of density and play with different combinations.

Getting rid of the sand as filter media also allows me to modify that last chamber and lower the pump to the bottom of the sump, as suggested here.

You've also shown that terrestrial plants are more efficient at consuming nitrates, phosphates, etc than aquatic plants. So I'll abandon the soil & sand from the refugium chamber. I have a ton of Pothos and Wandering Jew that has propagated water roots. I will anchor them in the refugium section and let them grow out of the sump.

I understand I won't grow enough plants between the aquarium and the sump/refugium to remove 100% of the waste, but I'm quite convinced it will help. I'm also not convinced there is anything else that would be a more productive use of that space. I'm still baffled that even though we've thoroughly discussed that this system, like most systems, will have more than enough surface area to host suitable quantities of bacteria without Bio-Media, yet it's still being suggest to add Bio-Media.

I'm also still interested in the simple "algae scrubber" idea, but replacing algae with Java Moss. Even if it doesn't do much for the aquarium, having a little built in Java Moss farm could be an asset in it's own right.


Thanks again to everyone who contributed here. And feel free to further critique or expand on what's already been said.

 

[jjohnwm]

I think it's worth keeping in mind that not every aspect of a filtration system needs to be designed and built for absolute 100% maximum efficiency. As you stated yourself, you aren't hoping or expecting to get away with absolutely no water changes, regardless of how great your filter is or how feisty your own particular bacterial colony grows. So...relax. Filtering a tank effectively enough to maintain excellent water quality...as opposed to a white-knuckled fist-clenching insistence that everything be absolutely state-of-the-art and tuned to perfection...is almost embarrassingly simple.

If you enjoy filtering water with your calculator taped to the side of the tank, by all means, fill your boots...but it isn't necessary. If you find that your own filter design reduces the accumulation of nitrate by 50%...there's no need to fret that it isn't a higher number.

Just a couple of quick comments: First, I think that Java Moss is a fairly poor choice for your quasi-algae-scrubber, simply because it is a very slow-growing plant. You want stuff that grows like wildfire and utilizes as high a level of nutrients as possible to do so; Hornwort, Guppy Grass, etc. I'm no plant guy, I don't keep many species, and Java Moss is one of those beautiful, tough, resilient plants that makes me look good by doing well...but, man, it is slow...

The other thing? Equally simple; you've mentioned a few times that you just don't want to stuff your sump with a huge mass of biomedia. IMHO, one of the huge benefits of a nice big roomy partition-less sump is that you can throw in one or several big-ass sponge filters to keep them cycled and ready for setting up new tanks at future times. So if you have a breeding surprise, or need an emergency hospital tank, or a quarantine for an unexpected addition, or you keep those truculent anti-social jerks called "cichlids", you can put together a new tank that is largely or completely cycled (depending upon the bioload) in minutes with little or no notice. Well worth the horror of needing to look at all that bio all the time...