Backyard Aquaponics
A place to discuss aquaponics

Ok, not a siphon as such?.... just a standpipe with holes that drains continually... correct??

Any idea how long it takes to drain from a certain level over a certain time of pumping...

ie... if it takes you 5 minutes of pumping to fill to a certain level, then mark it and turn off the pump and time how long it takes to completely drain the bath tub......

These are your effective limits...... obviously if you pump continuously at a rate almost equal to the rate you are capable of draining you tub will maintain a level of saturation that may be too high for your plants and/or too low in oxygenation....

Are you currently running your pump on a timer?

Do you intend to??

yes you are correct
it took about 3 minutes to fill less if I remove the garden hose,and it is still dripping after 2 hours

Ok... so your options are.... stay with the timer and perhaps drill more holes in the standpipe to increase the speed of the drain.... thus allowing more timer "cycles"....

Or leave it as is..... bearing in mind your location (Gold Coast) having the growbed stay moist for a longer period of time (certainly in summer) might not be a bad thing....

Question is... will it provide enough oxygen for the plant roots.... probably... and will it provide enough turnover/oxygenation of your pond?

Obviously, with thise figures you could only get about 12 cycles a day....
bath tubs are I think about 200-300ltr ....; so that's about 2400-3600ltr turnover a day.

yes is that the right thing to do it has 6 times it can switch on and off

I only have very thin layer of media due to my admittably less then optimal design, you are using 100mm for your water supply, i am using 150mm for my growbeds, all of my root systems are shallow so I need to flow for longer.

The other option, if you want to increase your turnover rate and total capacity would be to ... increase the number of tubs/growbeds.... and/or install a "bell siphon" in a standpipe.....

The "bell" siphon would allow you to pump to a predetermined level, which would then initiate the siphon and rapidly drain the tub.... i.e. it might only take 3-5 minutes to drain....

Obviously you could then either run your pump coninuously (if need be bleeding some pump capacity off {and providing extra oxygenation} by using a "fountain" bypass) or run many more cycles per day

If you're using or going to use a timer then I think you probably need to invest in one that will do at least 12-20 times per day....

This means you could extend your timer cycles out a bit, mine is no longer dripping after 10 minutes, you only need to wath your oxygen levels in the water - aerators are a good idea.

bunnings sell a hpm timer that can do 15 min cycles for 4.95

I have an older style timer that has 1/2 an hour intervals?

if youre still dripping after 2 hours... 15 mins on, 1 hour off would be a good place to start

Other option then Hunter is to add another tub and double the capacity within the same timer cycle..... ie. you'll pump for the same length of time (roughly) but fill two tubs (twice the capcity) while still taking about the same "drain" time....

Doubling your turnover capcity/day.... With me??

Also gives you twice the growbd capcity (hence filtration) and potential plant production... and allows for more and/or bigger fish ...

yes but isnt there a amount of flow which is the best for the plants?

afaik the flow is not a major problem providing the media is not washed away - they just need a bit of time with their roots not submerged. They need to get wet nutrients, then just stay moisty for a while, then more wet nutrients.