Is a biofilter supposed to be outside the pond?

[Lumka]

Hi, I have a 1300 gallon pond, and I am planning to build a DIY biofilter. As I am searching the net - it seems that in all the designs the filter is outside the pond. Is there a reason for this? My plan is [was] to make a submersible filter, but now I have my doubts. Can someone please be so kind as to tell me what is wrong with my logic?

What I plan is a tote box, sitting on the bottom, connected to my pump. Forgive my hand drawn diagram! I have a 2000g/h pump, and was planning to line the tote with filter sponges --> bioballs --> carbon.

The reason I have for making it submersible is to hide the setup, and not have an eyesore outside.

I would like any suggestions, please.

 

[Tula]

My first pond had a similar type filter, an all in one box that rested on the bottom of the pond. It seemed to work ok, but it was not easy to remove and clean.

I believe one reason the bio filters you see on line, are often outside the pond, is they require the presence of air. Lots of people make baki type showers and use them as water falls.

 

[Mmathis]

Like @Tula said, ease of cleaning and introduction of air.

 

[Meyer Jordan]

In addition to what has already be said, your biofilter design in itself does not allow for ease of maintenance. Activated Carbon in a biofilter can be quite beneficial in removing certain pollutants but effective lifespan is, at the most, a few weeks. At which time it will need to be completely replaced. Not easily done with your design.

 

[morewater]

A tote box will weigh quite a bit when it is filled with soaked sponges and soaked carbon. Lifting this box out of the water in order to clean it will most likely result in it "bending" and spilling the contents out into the pond, thereby re-releasing the contaminants that you so diligently "collected" back into the water column.

Any above-ground, below-ground or hybrid bio-filter construction needs to be of rigid material, be easy to drain and clean.

Barrel bio-filters (40gal, 55gal) can easily be dug into the existing landscape to reduce their visual presence and can quite easily be disguised with stone and plant materials while still being relatively easy to service.

Sponges, while they may work are an absolute pain-in-the-posterior to clean as they each have to be cleaned individually and tend to re-clog rather quickly. You're better off with a hard substrate such as bio-balls or some such other easily-cleaned material. Lava rock is in the same category, it's heavy, clogs up quickly and isn't easy to clean.

Matala mats (when used in successively decreasing pore sizes) will trap the vast majority of the suspended detritus. Furnace filters, floor scrubbing pads, etc. are either too fine a mesh or too large a mesh. Do it once and do it right.

If you're going to go the barrel route, ensure that the barrel is of "food grade" material meaning that it wasn't used originally to transport solvents, etc.

A final thought, a "bottom up" design is more efficient than a "flow through" design. Gravity is your friend.

 

[Lumka]

Thanks all for the feedback! I especially like the comment: do it once and do it right. Appreciate it!

 

[Usman]

welcome , use gravel if u want thats best underwater filter since water will go thru it easily and will not get clogged for long time as used in aquariums and you dont need to take it out to clean it , sponges are used mostly where it can be easily cleaned since its mesh is finer and will catch even the finest debris , it wil get blocked too quick to pass water properly
i have read some where bio filter needs to be near the surface within a 10 inches to function at its fullest , may be u can place some hollow blocks below and raise it like a bog inside pond corner , i have seen submersible filters for polishing water as you want but they are made on smaller scale like in buckets that can be taken out

 

[budgenator]

In pond bio-filters work okay, but they are a PITA to maintain! Every weekend you have to pull them out and wash out the foam, and it just kills your weekend. I gave up on them when I realised I was seriously contemplating building a crane attachment for my lawn tractor to pull those heavy things out of the water.
Now everything I do is measured against 1. is it easier and 2. is it better. I know if it isn't easier, I'll put it off so it doesn't matter if it's better. I'd love to get my weekly pond maintenance down to 20 or 30 minutes, more time for enjoying the pond.
At 1300 gallon pond, you're going to want 130 gallons of filtration, by adding plants you can cut back the filtration a bit, Goldfish don't need as much filtration as Koi do also.

 

[Meyer Jordan]

At 1300 gallon pond, you're going to want 130 gallons of filtration,

How do you arrive at this figure?

 

[budgenator]

How do you arrive at this figure?

I assumed it was a widely recognised rule of thumb, http://www.koiphen.com/forums/showthread.php?127398-Pond-and-construction-forum-101
http://www.matalausa.com/How-Much-Matala/How-Much-Matala-Will-You-Need-p-68.html
it's overkill if your using Matala and a K1 MBBR but he's talking sponge pre-filter and bioballs and AC all in one tote filter.

In fact Lumka, look into getting green Matala or even better green and blue http://www.matalausa.com/Matala-Filter-Media-Info-c-26.html to use instead of the sponge filter, you'll be much happier with it. If matala is out of your budget range, you can still design to use a 1/4 sheet of matala sized filter, and locate a sponge the same size so it's easier to upgrade later when your fish get bigger.

 

[Meyer Jordan]

I assumed it was a widely recognised rule of thumb, http://www.koiphen.com/forums/showthread.php?127398-Pond-and-construction-forum-101
http://www.matalausa.com/How-Much-Matala/How-Much-Matala-Will-You-Need-p-68.html
it's overkill if your using Matala and a K1 MBBR but he's talking sponge pre-filter and bioballs and AC all in one tote filter.

In fact Lumka, look into getting green Matala or even better green and blue http://www.matalausa.com/Matala-Filter-Media-Info-c-26.html to use instead of the sponge filter, you'll be much happier with it. If matala is out of your budget range, you can still design to use a 1/4 sheet of matala sized filter, and locate a sponge the same size so it's easier to upgrade later when your fish get bigger.

Using rules of thumb can be dangerous because they usually have no basis in fact and may result in the "thumb" being in your eye or stuck up some other unmentionable location. They are entirely too vague. I am especially leery when the author can not even spell-

• 10 % pond volume in filteration (sic) volume

• 1/3 of total surface area of pond = surface area needed for fliteration (sic).

(From the Koiphen link).

And even though it is reasonable to assume that Matala knows what the SSA is of their pads, even they are vague in the use of terms like light. medium and heavy fish loads. These terms are subjective and open to individual interpretation.

 

[Gordo33]

Using rules of thumb can be dangerous because they usually have no basis in fact and may result in the "thumb" being in your eye or stuck up some other unmentionable location. They are entirely too vague. I am especially leery when the author can not even spell-

• 10 % pond volume in filteration (sic) volume

• 1/3 of total surface area of pond = surface area needed for fliteration (sic).

(From the Koiphen link).

And even though it is reasonable to assume that Matala knows what the SSA is of their pads, even they are vague in the use of terms like light. medium and heavy fish loads. These terms are subjective and open to individual interpretation.

What rule do you follow for determining the amount of filtration necessary for a goldfish or a koi pond? When I built my goldfish pond I was advised by several members of a pond forum to use the 10% of pond volume as a general rule. It seems that's a consistent consensus from multiple sites. To date it has worked keeping the water clear and all water test results where they need to be. I am considering adding a koi pond this year and am interested to here your thoughts.

 

[Meyer Jordan]

What rule do you follow for determining the amount of filtration necessary for a goldfish or a koi pond? When I built my goldfish pond I was advised by several members of a pond forum to use the 10% of pond volume as a general rule. It seems that's a consistent consensus from multiple sites. To date it has worked keeping the water clear and all water test results where they need to be. I am considering adding a koi pond this year and am interested to here your thoughts.

I will cede the fact that if, indeed, one was to follow the 10% capacity rule they would probably not encounter any problems, but the real question is how many pond owners really follow this rule. For a pond with a capacity of 1000 gallons this means that the biofilter must, according to the rule, have a capacity of 100 gallons. I can truthfully say that I don't believe that there is a commercially manufactured biofilter presently available that has a capacity of 100 gallons that is logically affordable for a 1000 gallon pond.. I seriously doubt that any pondkeeper is going to spend more on the biofilter module than they did on the entire rest of the pond including the fish and plants. But if they do, I grant you that they would have enough SSA to support quite a number of fish.
This, of course, does not include "bogs".

 

[Gordo33]

I will cede the fact that if, indeed, one was to follow the 10% capacity rule they would probably not encounter any problems, but the real question is how many pond owners really follow this rule. For a pond with a capacity of 1000 gallons this means that the biofilter must, according to the rule, have a capacity of 100 gallons. I can truthfully say that I don't believe that there is a commercially manufactured biofilter presently available that has a capacity of 100 gallons that is logically affordable for a 1000 gallon pond.. I seriously doubt that any pondkeeper is going to spend more on the biofilter module than they did on the entire rest of the pond including the fish and plants. But if they do, I grant you that they would have enough SSA to support quite a number of fish.
This, of course, does not include "bogs".

Agree with the expense but a 100 gal Rubbermaid tank cost me $95. Stocked with yellow flag iris and 50# lava rock in a laundry bag wrapped in quilt batting to prevent clogging added approx $25. Plumbing approx $50. Plus an 8 foot long x 4 wide stream planted cost $25. Grand total $195. DIY affordable and so far very affective.
So are you saying commercial available biofilters that are affordable would hold a smaller volume of water. How do you determine the proper size biofilter ? What makes one biofilter better than another?

 

[Meyer Jordan]

One method for determining the minimum required level of biofiltration is determined by total fish mass. Ideally, future fish mass should be the guideline as fish will grow over time. Another method advocates using the amount of feed offered daily as the base line, but, although this will give a more conservative result, it does not account for fish producing Ammonia through respiration EVEN during a prolonged state of fasting.
To cover one's tracks, so to speak, I would advise using both methods and use the result that indicates the higher required SSA for complete Ammonia conversion.

The fish mass only method is generally described at this link-
http://www.russellwatergardens.com/calculations/how-many-fish-can-i-have-in-my-pond/

The feed method is described in this document-