Filter Questions

[Devoid]

So I had been using a filter made of window screen made for pet claws. I ended up with tilapia in the grow beds. Got them out, more fish, got them out, more fish. I don't know if eggs are getting through or if somehow eggs have been hatching from the previous batch that I got out that somehow survived without the mother.

I'm building new fish tanks. Going from two 6 foot round, 2 foot deep tanks to 4 foot by 8 foot by 5.5 foot deep tanks.

I'm wanting to put in a radial flow filter but can't find  information on proper sizing for diy. I see one place that says retention of 2 minutes, and everywhere else says can't be too fast but can't be too slow without any word on how to properly size one.

What is the best way to make sure no tilapia eggs get into the grow beds again? I've lost way to many crops due to the tilapia

752sq feet of grow bed trying to make small scale commercial work to test the market.

[Jeff S]

The formula I use to see how long the water is retained in the filter before moving on is:
Size of filter (in litres) / flow rate (in litres per hour) = Retention time in hours. 
(Same can be done in gallons & gallons per hour)
For our system the equation looks like this..
50 / 2700 = 0.0185 of an hour or 1minute 7seconds
To help you out here is a handy Decimal to Time Calculator
http://www.calculatorsoup.com/calcula...

Hope that info helps some out there interested in setting up a solids capturing RFF..

[Devoid]

I understand how to calculate how long water is retained given a size, or how to calculate what size for a retention time at a flow rate.

The question is the ideal retention time

[Jeff S]

My bad. I think it depends on what percent of the solids you're trying to pull out in the filter. I don't think you'll ever filter out all the solids with simple home made filters. There are many methods to remove fine particles. Stuffing bird netting in the radial filter or in a second filter will pull out a lot of the fine solids but have to be cleaned regularly. Bio filters are necessary for converting ammonia but the media is pricey. If you have the space put in a media bed (simple as the bottom of an IBC tank). This will act as a bio filter and a fine solids filter. The deeper the better for filtration.No need for drain and fill just water in on one end and out on the other with 1-2" of media above water level.

[George]

This is food for thought:  Make your own biochar (free except for your labor, using found wood) and use that in a media filter with worms.  No gravel, plastic, or clay on earth has more than a small fraction of the surface area of biochar so you can get much more filtering with less volume of media, comparatively.  .  There are many ways to make it but none more simple than to dig a hole in the ground and build a fire in the bottom.  Slowly add wood until the hole is full of coals, then extinguish.  Then, crush, screen and rinse as you deem necessary.

Jeff S said:

 Bio filters are necessary for converting ammonia but the media is pricey. 

[Devoid]

Do you have to replace the biochar?

[George]

I doubt it - I've had one filter going for about a month and see no indication that the char is breaking down.

[Devoid]

If you grind it, how do you contain it from flowing out with the water ?

[George]

I use a standpipe with gravel guard - media bed 

I first screened and rinsed through 1/4 inch hardware cloth to remove fines, then screened through 1/2 inch to exclude larger chunks.  

[Jeff S]

I looked into biochar before but for my dirt garden. Seems simple enough to make since I use a wood heater in my GH. I wonder if it could be mixed with growing media in a bed to increase filtering capabilities?

[George]

I plan to use it in that way but will leave a dry layer of gravel on top to ensure that moisture doesn't wick to the surface of the media.

Jeff S said:

I looked into biochar before but for my dirt garden. Seems simple enough to make since I use a wood heater in my GH. I wonder if it could be mixed with growing media in a bed to increase filtering capabilities?

[David Marland]

I designed this filter when I was just starting out, after watching hundreds of you tube clips on water features, coy ponds and then stumbling onto IBC aquaponics. I have been using it for over twelve months now, it works a treat.

https://www.youtube.com/watch?v=goaKIt_JObo

I have a few times now used a house hold broom to clean the sides of my sump tank and fish tank to remove algae. To clean the filter of solids you just turn the bag inside out and use a garden hose. Its basically two radial flow filters working together with a paint bag filter collecting any extra waste. Or in your case fish eggs! they are fully aerated due to water flow and the excess food waste is collected too. I can run it at 600ltr per minute or approximately 125gallon per minute, but I don’t need that much filtering really, so I run it at 400ltr per minute around 75 gallon per minute?

You can tell when the bag needs cleaning, when water starts to appear on the lid off the filter.

But today I was thinking of ways to improve it more.