Wadly’s Biofilter

Wadly's fish (click to enlarge)
Some of Wadly's fish (click to enlarge)

Terry (aka Wadly) has a beautiful tank of fish (too many fish for the tank, but I won’t say anything if you don’t say anything) which needed a better filter. The filter I was replacing was a cobbled together job of  filter material wrapped around the pump and held in place by a piece of support hose. This assembly needed hosed off a couple times a day to keep the pump pumping and the algae in control.  Having to hose it off a couple times a day, more when it was really sunny, sucked.  I always managed to get my feet damp.  Ugh.  This filter was SO not working for me, the one who stayed home and hosed it off.  Ugh.

By now you should know me well enough to know I like to plan smarter, not work harder.  I like to automate everything I can. So, biofilter here we come.

My friend Mindy has a biofilter which consists of two sizes of rock (small drain and pea gravel) layered in a vessel under a layer of filter medium.  The tank water is pumped into the bottom and rises through the drain rock and pea gravel.  Anything needing filtered is trapped in the gravel below the filter medium and the filtered water is returned to the tank via two frog fountains.  Cute.  She has a spigot plumbed into the bottom of the vessel to drain the sludge when the filter becomes plugged.  Cute AND functional.

Biofilter (click to enlarge).
Biofilter (click to enlarge).

But my problem is a bit different.  I have to filter AND I need to moderate some of the tank’s nitrates.  I have enough nitrifying bacteria to do the conversion from ammonia to nitrite to nitrate, I just need more plants to consume the nitrate.  Wadly doesn’t want more plants in his tank.  He wants to be able to see his fish.  And he won’t let me add a grow bed (what a Scrooge), so an open topped biofilter was the next best answer.

If you enlarge the photo, you’ll see how I handled the problem of roots plugging the overflow.  I cut the top and bottom off an Aquafina bottle, drilled a hole in the side to attach it to the bulkhead fitting using an additional rubber washer.  This works really well.  The roots can get into the outflow screen but aren’t long enough to get into the bulkhead fitting and plug it . . . yet.  I should have left the bottom on the bottle and drilled big holes in the bottom or used a larger bottle or both. I’ll keep playing with this until I get it just right.

My test biofilter  isn’t very pretty, but that will come.

I got two foam half-barrels from Rite Aid for $10 each at an end of season sale.  I think that’s a heck of a buy as they are regularly $39.95 each. I will use one for the *pretty* biofilter container.  The foam is too thick to use one of the neat rubber bulkhead fittings for attaching the pump.  I either have to buy a different kind of bulkhead fitting for that bit or glue the fitting into the drilled hole using eaquarium sealer.  I’m voting on the aquarium sealer.

So here’s the interesting bit.  I don’t have any gravel or filter medium in this biofilter yet.  The plants roots are trapping the particulate matter as the water is pumped through.  I don’t know if this is a sound long term solution but for now it’s working and working well.  I’ve already had two plants in the biofilter bloom, so they’re liking the nutrient flow.  One of the water hyacinths put on a showy display and one of the duck weeds blooms a tiny little white spiky flower.  I didn’t know those suckers bloomed!

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