Filtration for 100+

[Gideyon]

I'm not asking this because I need it.  It's more to understand and learn. 

Many years ago (1990s) my brother and cousin setup a 100g community tank at our house. The only filtration was an undergravel filter. They always had a clean tank and never had a sick fish. 

When I researched filters for a 100g tank, with the exception of one HOB, all were canister filters.  No mention of an undergravel option (granted, some fish don't do well with gravel).  

I know there's a divide among fish keepers on undergravel filters.  Some swear by them. Some refuse them. 

So assuming gravel is the substrate being used, what are your thoughts on effective filtering for that large of a tank?   Is one better than the other?  Is one overkill?  

Does anyone have experience with both? 

I know bioload is a factor as well. I'm not sure what assumptions to make to make it a fair comparison.   

[Daniel]

In a large aquarium there is a lot of surface area for beneficial bacteria to live an on. What that means is that for a large tank that is not overstocked the filtration needs might be very minimal. On my 500 gallon, it is mostly hardscape with minimal plants. The result is no filter at all is needed. I use a recirculating pump, but other than that nothing.

Adding sponge filters or canister filters would be overkill and add nothing except noise and expense. Neither one would improve water quality.

[Gideyon]

1 hour ago, Joseph said:

I have a 125 and I have two canaster filters one hob and two sponge filter as well as alot of plants and other than topping it off once a week I don't have to do water change but maybe once a month. Honestly don't have to do that my parameters are still perfect I just do it to promote spawns as well as replace old water 

A breeder tank?   I imagine with that many filters it's not a display tank.  How often do you need to rinse the media? 

[Gideyon]

1 hour ago, Daniel said:

In a large aquarium there is a lot of surface area for beneficial bacteria to live an on. What that means is that for a large tank that is not overstocked the filtration needs might be very minimal. On my 500 gallon, it is mostly hardscape with minimal plants. The result is no filter at all is needed. I use a recirculating pump, but other than that nothing.

Adding sponge filters or canister filters would be overkill and add nothing except noise and expense. Neither one would improve water quality.

First off, that is an amazing tank. 

How many fish do you have in there? Discus?  Do they use the whole tank? 

Do you do water changes or is the plant sufficient for nitrates?  Just wondering how you maintain something that large. 

As for filtration, I understand what you're saying with the bacteria.  But normal debris from waste or uneaten food, or even plants, how do you get those out?   Or do you let it decompose completely and let the beneficial bacteria take care of it? 

 

[Daniel]

31 minutes ago, Gideyon said:

Do you do water changes or is the plant sufficient for nitrates?  Just wondering how you maintain something that large. 

As for filtration, I understand what you're saying with the bacteria.  But normal debris from waste or uneaten food, or even plants, how do you get those out?   Or do you let it decompose completely and let the beneficial bacteria take care of it? 

 

There are never any nitrates as the tank cycled 13 years ago. I do water changes occasionally because I use this tank as the source of water for all my other aquariums and their water changes. But I don't think this aquarium would ever require much of a water change to get rid of nitrates or whatever. As I said though the water does get changed, because of the other downstream aquariums.

As far as waste or uneaten food, I think the bacteria just cycle it. I don't gravel vac it and the is a bit of mulm but it is not unsightly. I think aquariums left on their work better than people realize or are willing to try. Since it is rarely attempted everyone assumes it doesn't work, but at least this one experiment shows it is possible.

[MJV Aquatics]

Undergravel filters can be very great, or very bad depending on how they're managed. UGF's were all the rage in the 50's & 60's but fell from favor as power filters and canisters came along. Originally with a minimal air flow they were very good. But somehow it got sold that more filtration was better, so air flows were increased and/or powerheads were added...pulling much more detritus deep into the substrate. Without routine serious gravel vacuuming, they became a nitrate factory.

The best aquarium filter is really a few inches of sand for the substrate and plants, especially fast growing floating plants.

Somewhere...somehow...it became parroted that more filtration is better. I've lost track of how many times that I've seen "there's no such thing as too much filtration". But good filtration is about how well we filter water, not how much or how fast we force water through media! The dirty truth about filters is that filters aid in water clarity, but not water purity. Detritus trapped in the filter decomposes and pollutes the water...and more powerful or additional filters don't change this. Powerful filters and many filters is just a waste of money and energy.

So you might use an under gravel filter with gravel or sand (with sand you use landscape fabric between the plates and the sand), but ensure a gentle flow of water through the substrate (I have another article about Dr. Kevin Novak's video about using plenum's in the FW aquarium). You definitely want to add plants, especially fast growing plants that use ammonia as their N2 source. Later, if necessary, you might add an Aquaclear, a Tidal HOB or a modest canister filter. 🙂

Footnotes:

WRONG = "there's no such thing as too much filtration."

RIGHT = "there's no such thing as too much fresh, clean water."

[Gideyon]

18 minutes ago, Daniel said:

There are never any nitrates as the tank cycled 13 years ago.

OK... This might be an ignorant question but apparently I misunderstood the nitrogen cycle.  How can there never be nitrates unless there's something to consume it?   

[Gideyon]

5 minutes ago, MJV Aquatics said:

I wrote an article on my website/blog about the best aquarium filter is really a few inches of sand for the substrate and plants, especially fast growing floating plants.

Can you give a link?    I'm interested in reading that. 

[MJV Aquatics]

1 minute ago, Gideyon said:

OK... This might be an ignorant question but apparently I misunderstood the nitrogen cycle.  How can there never be nitrates unless there's something to consume it?   

Ah but there is.... IF there are sufficient fast growing plants they will consume  and covert ammonia into plant tissue...so the ammonia is not oxidized into nitrites, then nitrates.

Under certain circumstances, anoxic/anaerobic bacteria can oxidize nitrates into  nitrogen gas that escapes harmlessly. (although creating such an environment can be challenging in the highly oxygenated FW aquarium.)

[Gideyon]

@Daniel, when you decide on the number of fish and their respective bioloads, are you eyeballing it to make sure it doesn't produce more ammonia than the tank can handle?   Or is it so high that you have nothing to worry about? 

Like if you were to put cichlids in there, who have a big bioload, in order to keep your tank's self sustaining bio filtering, do have a "formula" in your head of how many the tank can handle, or you just have a hunch of what it can handle? 

 

[Daniel]

Honestly, it is all mostly hunches.

I usually don't track water chemistry because I don't have to.  Which means I am just eyeballing it because most established aquariums can handle fairly high bioloads.

I don't think of it in terms of fish though. I think of it in terms of fish food.

The big aquarium with 12 discus that I am feeding constantly has a much higher bioload than the exact same aquarium with 75 angelfish that I feed sparingly. Beneficial bacteria can double their population size in 24 hours if the nutrients are there to support them. And then double again if need be.

So if there is a formula, it is this:

Food in = Waste out.

[darkG]

On 3/7/2021 at 8:35 PM, MJV Aquatics said:

Ah but there is.... IF there are sufficient fast growing plants they will consume  and covert ammonia into plant tissue...so the ammonia is not oxidized into nitrites, then nitrates.

Under certain circumstances, anoxic/anaerobic bacteria can oxidize nitrates into  nitrogen gas that escapes harmlessly. (although creating such an environment can be challenging in the highly oxygenated FW aquarium.)

I agree.  Additionally, If there is enough demand for ammonia, plants may resort to feeding on nitrates. (I think Daniel's message may have been confusing; obviously a tank can be cycled and produce excess nitrates). 

[Daniel]

13 minutes ago, darkG said:

I agree.  Additionally, If there is enough demand for ammonia, plants may resort to feeding on nitrates. (I think Daniel's message may have been confusing; obviously a tank can be cycled and produce excess nitrates). 

Yes, sometimes I don't even understand what I say.🙂

[Anita]

On 3/7/2021 at 12:09 PM, Daniel said:

There are never any nitrates as the tank cycled 13 years ago.

THIRTEEN years ago? OK, that is.. just... f***ing AMAZING!!! 😲 Sorry for the outburst.

[darkG]

15 minutes ago, Daniel said:

Yes, sometimes I don't even understand what I say.🙂

I know, right? But I think that is because we are too damn smart so that even we, who are really smart, can't keep up. That's pretty waterproof, I'd say. 🤪