Backyard Aquaponics
A place to discuss aquaponics

I forgot to mention that they where alive and wriggling.

If it has been dead a while, it is hard to say that what you found on it had anything to do with the fish death. At a glance they kinda look like midge larva to me but kinda hard to tell. Midge larva are often found in tanks, especially tanks where the fish don't eat them all. They actually make really good fish food supplement, there have been studies that showed fish getting a little bit of midge larva in their diet actually had far improved feed conversion ratios than could possibly be explained by the small amount of weight of midge larva they got to eat.

Good to know, should I be able to catch them in a fine net? I will have a scoop around and see what I find.

Overflows all replaced with 50mm and plumbed straight back to the sump instead of to the next tank down, they can now handle constant flow in this arrangement, the only thing left is to install the solid lift's.

What is the best size for holes in the solid lift? I was thinking 8-10mm

The grate for a SLO drain should allow as much flow as possible while keeping all fish out. I actually usually use an atrium grate on the pipe for large set ups and a net pot for smaller pipes but I don't deal with fry. My fingerlings are usually closer to 3" when I get them.

If you are keeping fri in your IBC, I would recommend a floating fry net.

Im going to have a length of pipe that goes allong the bottom to the centre of the tank and put an end cap on to stop fish getting into it. I will guesstimate the number of holes to be drilled along the lenght and leave it on the low side to see how much it restricts the flow, install and watch can always add more holes if it can't handle the flow, I dont want so many hole that they reduce the velocity of the water entering the SLO.

No fry, not aware of any edible fish that we are allowed to keep in AUS, that can be easily breed in small tanks and can handle my temperatures. So untill the Koi get bigger its all good.

Make sure the holes are big enough to pass solids. Also I would suggest slits instead of holes. Round holes beg to be clogged.

Was going to use a 10mm hole should be large enough even for swolen 5mm pellets, I could however make them 10mm slits.

Cutting slits in pipe with a chop saw is far easier than drilling holes. Also easier to clean as needed.
As to the velocity, we are talking about a gravity drain, there is never going to be high velocity water entering that SLO drain unless you have set it up so that the water level in the tank rises high above the drain level to provide excess pressure. We are NOT talking about flushing a toilet here. The fish swimming, the water swirling about the tank and any air stones help keep your water mixed and moving about, hopefully with the solids tending to move closer to the drain where they can move out of the tank with the water and it flows. If you restrict the flow into your SLO enough that the velocity of the water entering the holes will be higher than simply having the pipe wide open, then you will actually find that the water level will start to rise in your fish tank because you are restricting the flow of water getting into the SLO and out of the tank and you might even experience an overflow, especially if some of your holes start to clog. (restricting flow might be able to increase pressure but ALWAYS at a cost, you must make sure that cost doesn't outweigh the benefits.)
I would say cut slits about half way through the pipe every inch across the bottom of the tank. That way the pipe resting on the bottom can only block a small portion of the slits and the solids that might loge against the pipe will have a better chance of being close enough to a slit to actually get sucked out of the tank with the flowing water.
Slits can be cleaned using a knife while holes require poking something into the hole and are more tedious to clean out.

Thanks for the advice TC.

I will put slots in the pipe to allow for max flow and more, I have also got T fittings so that if the bottom pickup gets blocked it will overflow into the drain line, allowing time for me to notice and rectify before I have a serious problem

I want to install siphons to that i can run the pump 24/7, I had a quick crack last night at making a bell siphon out of some scrap and added a 90 degree bend into the outlet from the GB, while i got it to fire i couldnt get it to break at the bottom, I will have a play with the 90 or perhaps 45's as well as the ammount of inlet into the bell to try and rectify this. the question is if the siphon fails to fire for some reason will the bed overflow or jusy run constant flood until sorted? or is it best to install say an emergecy overflow?

The only time I have ever had a siphon overflow was when I forgot about the tap running. The sump overfilled, and so did the growbeds. Otherwise, siphon failure means that it just keeps gurgling and gurgling. Most of the time it is because the media guard restricts flow too much, and water slowly but continuously trickles in.

I did notice the media gaurd causing a slow flow last night, going to have a better go at it tonight assuming i don't get scared of the rain and hide inside. Will also have the SLO's in tonight.

Had a productive weekend, got the new SLO's built and in and got siphons in and working in all beds, three are running bell's and one an affnan because i couldn't get it to break with a bell.

4mm sprinkler tube is no good as the air line on a bell siphon, I also think I need to put in larger media guards to allow more water flow.

Some new residents.