Sump with only sponge?

[Toby_H]

Bacteria will grow on almost any/every surface in the system. So we should expect an extremely thin layer of them over virtually everything.

With the exception of breeders who overstock bare tanks with no substrate for growouts, I doubt any of us have ever had a tank that had insufficient surface area to house enough bacteria for a proper nitrogen cycle even if we removed all of our "bio media".

Sponge only filters certainly will work. And as the filter clogs in one area, wherever the water continues flowing will just get more bacteria in that area.

 

[thiswasgone]

Clogging… bacteria can produce an extracellular matrix which helps them survive and can clog, e.g., a sponge. But there are limitations — energy. The amount of energy left in uneaten food and faeces is limited. After months of growth, the population reaches a point where there is no energy to support further growth, only to sustain the colony alive. The only limitation is available surface area. If there is plenty of it, the medium is covered with a thin layer of biofilm, which is effective in nitrification and oxidation of dissolved organic carbon (wastes in the water). No clogging occurs at this stage. The bacteria can even digest their own matrix to obtain energy. The bacteria/protozoa are starving and readily clean the water. This results in the best water quality. There are some limitations — the entry surface, where plant debris and faeces are prone to clog the surface. There should be a balance between the entrance area and the amount of waste… but apart from that, everything comes down to the overall surface area of the media. If the overall surface of the media is too low, the growth of the matrix makes the biofilm thick and restricts the flow. If there is enough surface area, no cleaning is necessary! The filter is self-cleaning.

I had a 45 ppi sponge that clogged after a year, but only when my little son overfed the fish. About 800 cm² of entry surface for 4 grams of dried food per day. I guess the dose was doubled during the overfeeding period. I had static K1 before for 3 years — no maintenance at all — I just wanted to change something… now there are sponges.

To sum up… filtration is easy: enough overall surface area, enough entry surface, and the filter is maintenance-free. You can calculate it with this tool… check:
https://www.monsterfishkeepers.com/forums/threads/feeding-and-filtration-planner.765567/

You're 100% right in terms of the typical home/hobbyist aquarium which is also why I stated in my last paragraph everything is going to depend on how engaged the OP wants to be with his filter. Most fish keepers won't house enough fishes (small or large) to actually have to worry about min-maxing nitrification so they can maintain a good enough bio-filter with most high-surface area bio-media. Of course this might matter if space is a large constraint but overall you can just throw in some sponges and pass enough flow through them to get a 2-in-1 filter; no real need to have a polishing pad in a well establish tank with weekly water changes. I did this with a heavily stocked 180 I ran a long time ago, used a 55g tank as a sump and ran it with only ~1ft^3 worth of plastic pot scrubbers I got at dollar tree.

As long as you're not over-feeding or over-stocking it's fairly difficult to cause major issues with your bio-filter.

 

[thiswasgone]

So...you don't need to ask yourself a "plethora of other questions" before building a filter...unless you just want to. No need to lose sleep because your filter isn't 99.9% "efficient". Virtually all of us have a vast excess of surface area for bacterial growth in all of our tank/filter systems right now. That is, by definition, good enough. Zero ammonia is zero ammonia, period. More filtration, or more efficient filtration, isn't better than "good enough". Your water won't be better; ammonia readings won't go below zero ; fish won't be healthier.

Haha exactly.

Bio-filter media selection is pretty pointless for most home/hobbyist aquarium since most people severely over-estimate how much media they need at all. Unless someone is overfeeding and/or overstocking most setups will work so long as you properly cycle your tank & filter. Just keep a consistent water change schedule to maintain 0ppm for nitrates. You'll drive yourself crazy over what type of sump design to use as it will lead you down a path of endless potential optimizations.

 

[triamond]

In 2005, I had a planted tank and was testing various sources of nitrogen for plants. I was removing the media from the sump until there was none left. Then I reduced the flow through the sump. Ammonium sulfate was added by a peristaltic pump at a dose intended to achieve a target of 5 ppm NH3 in the water.

However, there was no detectable ammonium in the water — everything was readily converted into nitrates. I stopped the experiment when fish deaths started. Without media in the filter, the water became dull.

Agreed, the uncleaned internal surfaces of the aquarium and sump should be enough to provide surface area for nitrifying bacteria.
But nitrification is only a tiny fraction of what is going on in the filter. There should be 20–100× more surface area for all the life in the filter, so it is not surface-limited.

 

[David R]

duanes our native shrimp don't tolerate the warmer temperatures of tropical tanks unfortunately, many have tried before and it just doesn't work out. I've never thought of growing our local mangroves in pure fresh water though, but it is something I'd like to have a crack at now that you've mentioned it! I've never seen them growing anywhere other than intertidal zones where the water is pure salt or very brackish, but the pods are everywhere at this time of year so it's worth trying I guess. Could be cool for an outdoor pond if it works!

jjohnwm that was a good breakdown of that epic post from T thiswasgone , thanks for taking the words right out of my mouth, and thanks thiswasgone for crunching the numbers in such detail! Jjohn its interesting to hear you've actually experimented with how much media you can move before crashing the tank, I've often removed roughly 1/4-1/3 of the bio media from a canister on one tank to kick-start my quarantine tank for new arrivals with zero impact on the main display, which has made me wonder just how much more could I remove. Some seeded media from the main tank and a bit of driftwood equals instant cycle for the new tank. I can't even remember the last time I've cycled a tank from scratch (probably not this century anyway).

I think you (and others who have also suggested it) are right that almost all aquariums have vastly more bio media than is required on paper, but I guess that's better than not having enough. I'm still toying with the idea of the HMF sump but will definitely try incorporate some sort of planted refugium type chamber, A; to provide opportunity to keep a wider range of fish, and B; provide some additional filtration.

 

[phreeflow]

It seems everyone is saying the same thing in different ways and it’s what makes this forum so much more valuable and interesting than short-from social media. I appreciate the different approaches as it gives a fuller understanding.

So basically…the consensus is you can use whatever you want in the sump and it’ll work but for ease of maintenance, those sponges seem pretty compelling. In fact, I’m convinced enough to throw out a bunch of bags of nasty ceramic media and place an big order of sponges for my own setup. Thx all

 

[thiswasgone]

Agreed, the uncleaned internal surfaces of the aquarium and sump should be enough to provide surface area for nitrifying bacteria.
But nitrification is only a tiny fraction of what is going on in the filter. There should be 20–100× more surface area for all the life in the filter, so it is not surface-limited.

Yup, heterotrophic microorganisms do a large amount of heavy lifting and require much more surface area compared to the autotrophic bacteria but i've already put in a large math post in the thread; don't want to go too overboard and potentially off-topic to talk about microbiology haha.

 

[jjohnwm]

Mmmmm.....heterotrophic microorganisms....(doing the Homer Simpson drool....)

 

[skjl47]

I've done this experiment on more than one occasion, originally starting out more or less accidentally but later in a more controlled way. Even in a completely bare tank, my fairly sparse stocking levels withstood the removal of all of the biomedium with zero ammonia being evident afterwards. I had to push it to stupid levels of abuse...vast overfeeding, or an increase in stocking/bioload, or removing 75% or more of the biomedium all at once...before any ammonia ever showed up, and that would disappear within hours.

Hello; Early on in the first decades of my fish keeping I ran tanks with only air pump filters, air stones and the like. I used under gravel filters and still do. I used little in tank box filters stuffed with floss. I used sponge filters. I used hang on back filters powered by air bubbles. I used simple air stones with no filter media at all. I am not talking powerful air pumps. Just the sort a teenager could afford from mowing yards for a dollar a yard and other similarly paid jobs.

I experienced the slow transition from air operated filters to impeller run power filters. As far as I am concerned the current power filters would not have happened without the simple air run filters. The early Metaframe power HOB's moved a lot more water than the air type but they lost siphon pretty much every day. Not like modern stuff which will restart on their own. You had little plastic caps on a stick with which you could re-start the siphon. I always ran some sort of bubbler along with the power filters. If I had to use only one sort of filter for a tank it would be air run. Likely a sponge filter nowadays. I still have some survivor air HOB's and do use them in grow out tanks with fry.

When i use a sponge filter in a bare tank I rarely clean it. It eventually becomes mainly a weight to keep the air bubble source at the bottom. The sponge sort of gets "clogged up" I guess but something else happens. A story. Some years ago I bought a few common angel fish cichlids. Wound up with a breeding pair (did a thread on them on here) They always ate the eggs, so I set up a grow out tank. They liked to lay on live plant leaves so I would clip the leaf and put it in the grow out tank. I would weigh down the leaf and position a bubble stone close by to keep the water moving.
I also threw in a very mature sponge filter run by air. The idea being it would circulate water when I removed the leaf & air stone after hatching. Also wouldnot suck small fry in like a power filter. I raised a few batches of fry in that tank and never cleaned the sponge. Point of the story being the fry would graze on the surface of the sponge when they became free swimming. Not sure exactly what they found but the exposed surface of the sponge. I have some guesses. The sponge would be cleaned nicely during a period before they grew enough to take other foods. The sponge would get a bit fuzzy between batches of fry. It is more than a simple trash collector.

Back to the above quote. jjohnwm tells the story well. To the OP, run the sponge setup which pleases you. Figure it will work well along with water changes even with half the sponges. likely with a quarter of the sponges or maybe one sponge. Likely with half the cleaning frequency or perhaps no sponge cleaning at all.
Jeep up the water changes (WC) and likely all will be well. We have to do WC no matter what filters we use.

 

[duanes]

Agree with the above.
Since millions of beneficial bacteria can live on the head of a pin ,(or in a tiny HOB filter, or a little swatch of floss), its overkill to stuff sumps with tons of media.
I´m also from the era in the 50s when we used under-gravel plates, and fish lived pletty well.
It only gets sketchy when the aquarist crams an oscar or 2 in a puddle of a 50 or 75 gal that its becomes problematic.