An (excited) word about filtration - Filtration

niko · 12-14-2010, 12:23 PM

I got excited or something discussing cheap and powerful canister filters made in China. So I jolted down some words of wisdom. Could be an eye opener for someone.

A few details have been ommited. Like what kind of glue is best to keep your fish in one place after you hook up a crazy powerful pump to your filter and have 0 algae issues.

Here it is:

It really annoys me to see filters labeled "for XXX gal. size tank". That's the dumbest claim ever.

Virtually all canister filters on the market are equipped with motors that are completely inadequate. Or rather - the motors belong to filters that are at least 1/2 the size of the housing.

Here's how it works:
There is a publication, a scientific one, about the water turnover through a filter that will provide 100% filtration. Running 1 tank volume an hour through the filter does not mean you have filtered all the water in the tank once. That's because the water being sucked by the filter is a mix of filtered and unfiltered water.

So, to make this simple - the water in an aquarium needs to pass through the filter 9.2 times in order to be filtered 100%.

Ok, so for my 100 gal. tank I need a filter that pumps 900 gph? No. I actually need more. I need about 40% more flow because of the resistance of the filter media, hoses etc. So to filter 100% of the water in a 100 gal. tank once every hour I need a filter pump that runs 1200 gph.

Wow!

And there is something else. There is an optimal volume of the filter media in relation to the tank volume. It is 8-10% of the tank volume. So for my 100 gal. tank I need a filter that holds 10 gals. of media.

Another "wow"!

And of course there is more. The filter media area is important. Meaning that I cannot get the smallest cheapest canister filter, hook up a 1200 gph pump to it and cover all bases. Simply put the volume of the filter and the pump output need to match. For my 100 gal. tank I need a filter that holds 10 gals of media and 1200 gph pump. But these 10 gals of media better not be stacked high. They better be spread as wide as possible. The thickness should not be more than 6.5 inches.

Wow...

No, that's not the end. There is a scary part to it all too. The same bacteria that happily eats your fishes' waste and makes Nitrate from stinky and toxic Ammonia will actually do the opposite if the flow through the filter media is too slow. So on Monday my bacteria eats Ammonia and produces Nitrate. On Tuesday my filter is slightly clogged and some of the bacteria now makes Ammonia from the Nitrate that their buddies produce. On Wednesday... you get it - most of the bacteria could be making Ammonia.

More... The bacteria in the biofilter is not just bacteria. It's all sorts of animals that gradually evolve and establish themselves. Think of it as the History of the World. Civilizations rose and fell. It's never the same. Now imagine what would happen if someone swept the place clean every 100 years or so. Started anew. There will be no real history. No humans. No internet!!! My point is - when you diligently rinse your filter every week or every month you are doing exactly that - resetting the development of your biofilter. Harming it. What is right to do is to choose the proper media that does not clog easily and does not need frequent rinsing.

Yes there is more... but enough said.

All of that makes my head hurt. Because when I see filters labeled "for up to 290 gal. tank" it's as if we all understand the conditions. And we don't. I bet this is the first post that explains filtration somewhat clearly to you. I've been in this hobby since 1981 and only the last year heard about all these things.

Basically if the filtration is properly setup you do not need mechanical filtration. You will seldom fight algae. There will be wars and fails and victories that you will never see - your bacteria and Co. will take care of it all for you.

Or one can just enjoy this hobby. It is not said we all must do things "the right way". It's about having fun, right.

--Nikolay

Phil Edwards · 12-14-2010, 01:12 PM

Interesting stuff Niko! That makes a great deal of sense to me from a scientific/ecological point of view. I'm working on a reply.

Cheers,
Phil

Tex Gal · 12-14-2010, 03:15 PM

I saw a comparison study of flow in gph on the net between filters. It said basically that when you add right angles and such and don't use the assumed head height you will not get the same gph. It also said that all pretty much all the filters except the Eheims were rated empty without media. The Eheims were true to the average ghp rated but of course all were tested new and clean.

Your article was quite interesting...

PeterE · 12-14-2010, 05:25 PM

Really good article. Thanks for writing it. It got me kind of interested in setting up a gigantic filter for an aquarium to see how it worked. It seems to me that the many people, especially inexperienced aquarists, who diligently sterilize their filters are not only just wasting their time, but they are probably harming their aquarium too!

Quote:

The Eheims were true to the average ghp rated but of course all were tested new and clean.

Eheims are the best!

fishyjoe24 · 12-14-2010, 05:40 PM

gives me something to think about and gives me the answer to what is happening with me 55g. I only have a 205 rated for a 40 gallon it. flow is 180gph, now put media in the filter and I get it goes down to 120-150gph and the media is packed.... looks like I should find a 405 or another 205...

BobAlston · 12-14-2010, 08:14 PM

I believe an important decision is what kind of filtration you want done. If you want mechanical filtration, you will have to clean it somewhat frequently because it will clog by definition. That is why I prefer prefilters on my canister filters. I use a sponge prefilter on the intake. I can easily remove it and clean it out. I can rinse with chlorinated water as I am not concerned with bio filtration at that stage. That essentially leaves the canister as a bio filter. I don't clean it unless for some reason the flow gets too slow (because it does get some very fine particles despite the prefilter).

I agree that the bacteria in the filter (and everywhere in the tank) can and will change over time. Basically they change based on the conditions. If you have a lot of amonia, one kind of bacteria will multiply, consume ammonia and create nitrite. And another bacteria grows in the presence of nitrite to create nitrate. But in absence of food, these bacteria colonies fail.

And for us planted tank types, hopefully with a reasonable amount of plants vs. fish, there isn't too much amonia getting to the canister anyway. The end result may be that the canister mostly provides water movememt, so the ammonia gets to the plants, oxygen from the surface to the water column, etc.

Just my thoughts.

Bob

fishyjoe24 · 12-15-2010, 02:51 AM

another problem is my 55 was lightly planted. hopelly i can stuff it with plants, and get stuff growing... and maybe nitrobactor and nitrosonomonas aren't doing there job right....

Phil Edwards · 12-15-2010, 05:43 AM

Bob,

I've found I've had the most success using a method similar to yours (and Amano's). The best results I've achieved have come when using medium sized lava rock from Home Despot and only a single coarse foam insert.

Some brief thoughts on change in filter efficacy over time- As mulm accumulates in the filter it changes the flow dynamics within the canister. Over time we'll get increasing volume of organic-rich areas which receive ever decreasing flow of oxygenated water. Those are the zones of ammonia genesis. The short of it is, as oxygen decreases the microfauna start using nitrogen as their electron donor rather than oxygen and that leads to ammonia and other nasties. Add to that an ample source of carbon from the trapped mulm and microfauna that are tolerant of hypoxic or anoxic conditions have a field day!

Moral of the story? Use coarse media to ensure maximum throughflow and don't rinse your media in tap water. Oh, and keep that sponge media clean!

JeffyFunk · 12-15-2010, 04:50 PM

Quote:

Originally Posted by Phil Edwards

Bob,

I've found I've had the most success using a method similar to yours (and Amano's). The best results I've achieved have come when using medium sized lava rock from Home Despot and only a single coarse foam insert.

How did you set this up? Did you just take the lava rocks and place them into your filter? Did you crush them up before hand? (So they look like Amano's Bio Rio?) How about a picture of what the media looks like? This sounds like a really great filter media, but would like some more information before I go rip things apart...

freshyleif · 12-15-2010, 06:39 PM

Cool I like it. Niko you mention that it is important not to stack the media to high and the thickness should be no more than 6.5". Can you elaborate on this please. I love the info and thank you for all you have posted on this subject it has been a great education for me. I also have to admit that when filter makers label there products as "rated for xx amount of gallons I always wondered rated by who and how.