Yet another filter!

I started out like everyone else I guess.I built a pond,added plants,added fish.Then this strange thing happened.My water went GREEN.Oh no!What happened?Well actually nothing.You can take any container of water and left alone long enough will start to do the same thing.This a natural happening.There's this little thing called algae.A very tiny plant that when given enough sunlight and nutrients will literally explode in your pond.This is called an algae bloom.So how to you get the water to clear up?A lot of folks claim that all you have to do is add plants to clear the water up.The plants compete with the algae for nutrients More folks even say to block the sunlight to the algae and it starves itself.This is accomplished by using plants that either float on the surface(like water hyacinths)or plants that produce foilage that grows to the top of the water and spreads like a lily.So how much coverage?Most say 70% or more of the surface.So now you've got a ton of plants in the pond.You've got 70% or more of the ponds surface covered.But now I can't see my fish?I know they're there but with so much plant coverage they're just hard to see.So I cut back on my plants and now the green water starts to creep back.Here's where the filter comes in.Some folks seem to have a knack for ponds.They can get the right combination of plants,fish and not have a problem with algae.Not me!My pond gets direct sunlight all day.Which is good for plants themselves but is also good for the algae.The pond here is clear to the bottom.Thats approx 24".The water returning to the pond is clear as well.And the plants used in the filter are doing extremely well.I have four koi and who knows how many comets.Plus the assorted frogs that wander up and stay.I make no claims that my filter works any better than any of the rest.I'm just happy with the results and I thought I'd toss out my idea.

The way all this begins is thru an existing filter I already had but always seemed to clog easily.Not to mention a brand here I'll say that the pump is rated at approx 500 gallons an hour.The original filter casing is approx 12 inches square and about 3 inches deep with a type of big open mesh snap on lid.What I did was remove the original filter media,place a flat stone in the bottom to weight it down and then cut some of the leftover black plastic screening I had left to fit the inside of the container.The plastic screen acts like a prefilter so as to block the pea gravel in my plant containers from getting into the pump lines and blocking the pump action.Its now October and this is the only portion of the filter I've had to clean.And only twice all season.Here's a line drawing of how this portion looks.

I started with a 100 gallon stock tank.These vary in size from 50 to 300 gallons.What makes these tanks special is that they're designed for outside use.Plus the walls are thick.The tank I have has walls approx 3/16 of an inch thick.Problem with most storage containers is that they're designed for dry storage.For the most part this means when you add water or filter material such as sand the container has a habit of swelling or expanding.This makes getting a good seal almost impossible.Below is an image of the tank with the hole for the return to the pond showing.The opposite side contains a bottom drain that comes with these tanks also.

Next came the outlet back to the pond.I chose 3" PVC for this.You don't want to risk a chance that the outlet might clog and your tank overflow and drain the pond while you're away for the weekend.After carefully cutting the hole in the tank near the top I mounted whats called a closet flange to the tank.This was a 3" size also.Cost approx $3 versus using a bulkhead fitting in this same size.Cost approx $30.I sealed the flange with rubber cement and bolted it to the wall of the tank.Once the filter is in place from the flange you'd come out with 3" PVC use an elbow to turn the flow down.A short section of straight pipe.Another elbow to point it towards the pond.And then enough straight pipe to get the water to the pond.

Next for me was the hardest part.A lot of upflow filters have a settling chamber.The water enters the tank at the top.Usually thru another PVC pipe and fills the tank from the bottom up.The settling chamber allows for the larger heavier stuff coming from your pond to sink.This keeps your filter from clogging as quick.I needed something to divide the settling chamber from the next stage of the filter.What I used is called eggcrate.This is a plastic grid thats sold in lighting depts of most hardware stores.It covers flourescent lighting fixtures.The hard part to this (for me anyways)was cutting this to fit the tank interior.This stuff is brittle and needs to be handled carefully.But it seems to work great as a partition.This was the second most expensive portion of the filter.Locally this eggcrate runs approx $10 for a 24"X48" sheet.So careful when you measure and cut.

Next comes my additions to this filter.From my experimenting I'd noticed that small gravel(pea gravel)makes an effective coarse filter media.So I wanted this as a first step above the eggcrate.But the eggcrate is kinda weak for this type of weight and the openings in the crate are 1/2" in size so the gravel would slip thru.So what I did was make a PVC support to distribute the weight of the gravel and added some plastic mesh screen to keep the small stuff from slipping thru.Some might regognize this mesh as the same stuff sold as gutter guard for those of you with rain gutters on your home.I was able to purchase this cut from a 36 inch wide roll.Cost was approx $5.

What you see next is the inside of the tank.You can see the support for the eggcrate.The eggcrate rests not only on this but along the sides of the tank also.You can also see the the plastic mesh on top of the eggcrate.The vertical PVC is the way the water from the pond enters the filter.The 2" PVC has about 50,(maybe not that many but it seemed like it) 3/8" holes drilled in it at the bottom so the water can flow out easily.I debated on whether to anchor this pipe to the bottom and didn't.So far this hasn't caused a problem.Water is fed from the pond pump via hose to the top of this pipe which then fills the bottom of the tank and works its way upwards.

What I don't have images of yet is the actual filter media I used.From the last image above I added approx 2-3 inches of pea gravel.This is a little less than a normal 50lb. bag.This gave me a coarse filter.The next step was adding a finer media.What I chose here was a furnace filter.Before you scream out about this I can tell you that this is an all natural filter.Made from bonded hogs hair.This filter is also in my home heating/air unit.The only problem with this is it wanted to rise in the water.I had to use a few flat stones to keep it laying flat.Lastly I added plants.For me this was 3 water hyacinths which I've always liked but my Koi seemed to like better.Now they can't get to it.And several bunches of Anacharis and some Water Celery.This last plant has seemed to really overwinter well in the filter tank.The blue screen you see is actually the filter mat.In the upper left hand corner of the image below is the return to the pond.What I did here was use a leftover piece of the plastic screen to create a strainer.The filter has quite a bit of Fairy Moss in it.I didn't want it all running back to the pond.About once a week I thin it out and give it to the fish.

The image below shows another view of the interior of the filter.You can see the hyacinths,the anacharis,and one of the stones holding down the filter mat approx 10" below.The little bloom?Well if you've never seen it before thats what Anacharis blooms look like.Some pond books call this unimpressive.I disagree.

Ths is kinda a massive filter and might be a little large for most applications.Plus its difficult to hide well.Some sort of lattice would work well with this and still let you see the plants in the top of the filter also.Here's a line drawing of the complete filter.But in the time its been up and running so far I haven't had to clean it.And I won't unless I see some sort of drastic change happen.In the construction of the filter I used an electric jig saw and power drill.And its not a hard filter to build.By far the most tedious portion was cutting the eggcrate.The image below shows the growth of the plants shortly after the filter was up and running.By the end of the summer here the filter looked this way.

Water gardening is supposed to be fun in my opinion.I don't have a green thumb when it comes to plants or a wet one when it comes to the fish.I just like to view my plants and fish at the same time.I don't get involved in the discussions on salt,PH or a few other things.You're trying to recreate something that happens naturally in the wild.I don't recall ever seeing Mother Nature bending over a pond with a PH kit in hand!This doesn't mean I'm against any of the above.I just haven't seen the need here.Have fun!

 Since I made this filter I have went strictly with the water celery as the plant medium for the tank.The celery is very hardy and grows like crazy.The down side to this is that it developes a really massive root system which is good for the filtering overall but plays havoc with the furnace filter inside.With patience the furnace filter can be cleaned but since its relatively inexpensive it can be easier to just replace each season.I've also found that the plastic coating holding filter material together tends to breakdown after a couple of seasons also.I've had the same success with just increasing the amount of gravel and leaving out the furnace filter.But with this increased weight it becomes more important for some type of support for the eggcrate.

Another concern should be the decision of cementing all of the PVC joints.Our pets here have never really given the pond a second look.But recently we added a new puppy who did take notice.In the fall of 2001 I failed to notice that a little hyper activity around the pond happened to also jar loose a portion of the 3 inch PVC return to the pond which was not cemented.I came in from work the next afternoon to a pond with only about six inches of water left in it.I didn't lose any fish but it's a heart stopping event to see.So if pets or neighborhood critters have free access then it's also a good idea to cement the return lines to the pond.

If you'd like more info on working with PVC in the construction of the filter or my own experiences at cleaning out the pond then check these two pages below.