Backyard Aquaponics
A place to discuss aquaponics

Hmmm...what is causing this die-off: chemical, biological, mechanical...
So, they are dying with some missing scales... Shoot, that could be any of those causes: pump trauma, some disease, leaching from plastic, high CO2, other weird chemistry.

I'd try 25% water changes (but I'm fairly new here!). If water changes daily stopped the deaths I think that would rule out mechanical and biological causes and leave us with chemistry.

Most likely chemistry would be O2 or CO2, I would guess. Having the FT totally covered might cause this. An optimum airstone setup would be a large (2"? 3"?) pvc standpipe sort of thing with the return water running into it and an opening at bottom and at surface level to allow maximum aeration of returning water (O2 enters water best when dissolved levels are low) and aeration during non-flow times (bubbles would create a pump effect pulling water in bottom hole and out top). If this stops deaths it would narrow cause down to high CO2 or low O2 or chemistry caused by same.

A less likely chemistry might be leaching. A small daily or weekly water change would stop deaths if this is the cause.

Good luck

Well, given my setup, it would be really difficult to multiplex the return flow and air pump. I will definitely try uncovering some of the FT to allow for gas exchange, and maybe start water changes if that doesn't do it.

When I find my camera, I'll post pics of the deadies (if there are any more)

I was thinking something like this would minimize holes in the container (only 1 needed). Please, please forgive the drawing. The first had better lines, but labeling ruined it. *sigh*

I was thinking something like this might work with a chest freezer...nice, insulated, covered, sealed container.

Oh, the top of the pipe is sealed except for 3 holes...

My FT isn't THAT sealed . It has styrofoam blocks that are placed over the top.

OK, found my camera. So here's a pic of my seedlings. They're looking a little sad at the moment, I think from the lack of warmth in the water. But heaters came last night, and I put one in today (positioned so it won't break!).

Oh, and no fish deaths since I opened up the FT lid to allow gas exchange. 2 days and counting...

How is the 4:1 red:blue LED light working? Is it enough?

Makes sense that the lid need to let o2 in and co2 out. I was going to do the same thing, but you saved me the trouble

Well I run supplemental day spectrum florescent bulbs, so it's hard to say. Also, I think my flux density is too low for the GB area. But if you want non-scientific... seems to work good .

So far the gas exchange seems to have been the answer. I thought there was enough in the GB, but apparently not.

Another day and no deadies!

5 deadies today! But these are different. They all have stab or slash wounds. So I think something with claws was swiping at them.
Now I have to figure out how to animal-proof the area.

Here's a quick update. Basically, my system is sucking wind. My seeds germinate no problem, grow about 3 inches and then stop. Currently, I'm focused on 3 problems.

1, animals getting into my garage and messing stuff up

2, air temperatures are low (but spring is almost here!)

3, F&D cycle is too fast; 2 min F, 1 min D.

1 I am fixing. 2 I am waiting. For 3 I tried to slow the rate of fill, but the siphon pipe is too big. A slower fill results in the siphon never kicking in. I suppose this is one of the downsides of a bell siphon.

I'm thinking of sticking a thinner diameter pipe inside the inner pipe to reduce its cross sectional area.

Hey Tamo, maybe the light levels are not enough. My tub of gravel that is flooded and drained about 1" by a siphon every few minutes is not growing lettuce as well as my beds had before under the same light. I think it is because I used foil-faced foam insulation to bounce the light around better before and this isn't being used now. The plants only get direct lighting from the bulb and the rest goes out into the room. I think if the foil stuff were put around the bed again that the plants would grow as before. Or, maybe the shallow gravel is too wet - the siphon wets the gravel about every 7 minutes or so. The fix for that would be deeper gravel. How wet is the plant area?

I hadn't considered light levels. That would be pretty easy to fix.

If by wetness you mean the highest flood level, it gets within about 1" of the top. If you mean the rest of the environment, it's very dry in my garage.

I think DD is suggesting that raising your gravel level is equivalent to a longer "drain" period in a sense... longer interval between floods as well

i.e. the plants roots will be drier for a longer period as it will take longer to flood to the level of 1" below the media surface......

That way you don't have to alter your siphon, other than perhaps fine tuning the flow.

I have maybe 4" of vertical space available. I'd have to look to be exactly sure.

Assuming that's right though, that would be a 3.2 minute fill. It doesn't seem like that would be a big enough difference to me.