Backyard Aquaponics
A place to discuss aquaponics

Perhaps if you lift the pump and have a tight tolerance on the float valve, you can make it turn on and off automagically.

Considering VB's comments, I have bitten the bullet and replaced my "work horse" Grundfos pump (8000 LPH) with a pond master 3500 LPH pump and now have a continuous flow operation.

I have now moved from cycling the tank water through the grow bed once a day to approximately 24 times per day, so with any luck the water quality should improve and hopefully I can get the ammonia levels down. BTW anyone want to buy a Grundfos pump for $250 – nearly new and a 7 day timer with 14 on/offs per day?

I also have some more shells which I will crush and add to the tank with an aim of getting the PH up; presently it is stuck around 6.2!!!

Next have to tackle the Red Spider Mite problem……..

Sorry I didn't respond Marcus. If you haven't done so already you can see what I have done here.

Are you using an autosiphon now? If so, what type. Are you gravity feeding from fish tank to grow-beds, or just running the same as before?

That is an excellent set-up VB.

I have skipped the auto-siphon and gone straight to gravity flow from the grow bed to the tank, the new pump continuously pumps into the grow bed from the tank.

Removing the "standpipe" from the middle of the drain of the grow bed has enabled the water to drain extremely fast (approx 1L per second) so I assumed there was no need to employ an auto siphon too.

The outflow now creates a nice strong current in the tank, some of the perch seem to 'enjoy' swimming into it.

I will add some photos over the next day or so to show the new set-up.

Sorry - I had misunderstood. I though you meant you were running the pump continuously but using flood and drain. The question of F&D vs continuous flow has been discussed here often and generally F&D has got up as the winner. It has however solved your immediate issues - so well done.

Ta!

Of interest an RMIT Uni PHD student has concluded that a gravel bed with Continuous Flow when compared to Flood & Drain provides slightly higher crop yields (20% better growth) I assume this is because the roots of the plants are in constant contact with the water:

http://www.hydroponics.com.au/back_issues/issue83.html

Perhaps this link could trigger some discussion.

We have, in the past had quite lively debates about Dr Lennard and his methods........

Yep - been there, done that Marcus. I prefer to recount my own experiences - continuous flow is not the way to go IMHO unless there is a reason why F&D is not an option. Others will disagree.

To start with Marcus - you might find that the water follows a direct path to the drain and the water is not distributed well. This may result in issues regarding the effectiveness of your GB as a biofilter.

Also that article is using hydroponics flood and drain. We tend to use a slightly different method in that the grow beds are significantly deeper. Hydro F&D beds seem to be around 10cm deep while aquaponics tends to use deeper (30cm+) beds.

Nova

The abstract for this article suggests that good old "Maxicrop" liquid seaweed can suppress spider mites ....

Spider Mite Solution

Believe Joel uses Maxicrop, wonder if he's had a spider mite problem???

I wonder if it would be safe to assume that Seasol and Maxicrop are the same thing (ie: seaweed extract) but with different brand names?

I will experiment with Seasol tonight!

I am feeding 25 perch / 4 goldfish 3-4 teaspoons of "Ridley Native" fish food per day which I assume equates to above 40g (plus the odd
lettuce leaves/worms/bugs). The fish vary from 3 inches to 6 inches in length.

I see VB who has a similar size set-up and number of fish http://www.backyardaquaponics.com/forum ... &start=465 and is feeding 200-300g per day.

My fish always seem hungry, can I assume that I am underfeeding? Is there a rule of thumb to apply?

Assuming your filters will handle it, the rule of thumb I would use is to feed all they will eat in 15 minutes. Do that 3 times a day. The other rule of thumb I have for tilapia is based on size, and is a percentage of body weight. That's harder, but I use it as a checkpoint. At the size my fish are, I'm comparing against 10% of body weight per day.

I'd suggest actually weighing your food if you want accurate gram measurements. I have found that 3 teaspoons (American standard unit of measure, here. Equal to 1 Tablespoon.) is about 5 grams of the food I am using. Yours shouldn't be that different. I have 63 tilapia at about 2-4 inches, and am now feeding a total of 4-5 Tablespoons (20-25 grams) per day.

Marcus - the difference is that I expect my fish are somewhat larger than your. The larger ones would probably be 300grams in weight. How big are yous?