Backyard Aquaponics
A place to discuss aquaponics

Any advice would be most welcome.

We added trout around a month or so back (also some SPs in residence, mostly in the sump tank). From memory the pH at the time was approaching 8 and we put in lemons in an attempt to lower it a bit.

Since the last rains a few weeks ago there has been rain water to put into the system again (relatively low pH), though at the weekend they were topped up once with bore water (relatively high pH).
Last week and again this week fish have died. Last week only 1 or 2. This week starting Sunday 2, then 1 then 1. One of the dead fish this week had had its belly nibbled at. Reverted to rainwater. pH on sunday was 7.5. Since then 250mL lemon juice a day (around 3000L in the system). No deaths for a day plus.

NH3, -ite and -ate are all near enough to 0. Fish are vigorous and keen on eating. They are growing. Not gasping or anything like that.

Does anyone have any ideas?

what sort of tank is your rainwater coming out of?

Do you offgas your bore water before putting it in the fish tanks?

Sounds like hungry fish...I would stop worying about the pH, and jut keep them well fed.
Bouncing pH around just causes more problems.

I have no doubt that the rain has affected your fish (same thing here after big weather changes), but trying to change the pH will not help. Just let it go.

I agree that trying to adjust the pH may not be very effective. However, if you can off gass the bore water and adjust the pH to match the system water for a day or two before adding it to you system, that might be more effective than simply putting it into the system and then trying to adjust with lemons. If you have no other choice than to simply run the bore water into the system, you are better off doing very small tops ups more often and don't try to adjust it after the fact, simply feed more (as much as the fish will eat without spiking the ammonia/nitrite) and hopefully the bio-filter action of dealing with the increased feed rate will help to naturally and steadily bring the pH down. Adding acid directly to a system is rarely a good idea unless you know the exact amounts to use to adjust the pH .1 or less per day and can do it in a very slow controlled manner so as to avoid pH bouncing.

I also second the question about the rain water tank? And perhaps the roof it is collected with. Galvanized tanks/roofing can build up dangerous levels of zinc in water and trout are rather sensitive to zinc.

Thanks

I had wondered about food and have already started increasing the feed. There isn't any particularly easy way to off gas the bore water, though hopefully it won't be a problem for a while now. Next summer I may set it up so that it's less of a hassle to top up with bore water each time so it'll be easier to add less, more often.

What's the easiest way to test for zinc. the roof catchment is lazerlite and similar, some of it covered with shadecloth (that part has been there for ages and very likely has an interesting microbial community. The tanks are 3 x 6,000 to 8,000 L galv tanks - also getting on in years (maybe 20 years, not sure).

I have my fingers crossed that it's just food and that there will be no zinc issues.

I think you will have to take a sample to CALM or Water Board and from memory they will charge $60-70, if your rainwater is coming from a gal tank that can cause problems, and +1 for pH not being a problem, we have discussed that in a thread on pH that I started when all of my fish died, my pH has been as high as 8 and was lower than 6, but others have fish living happy in all levels, faye suggested in that thread not to change pH quickly as this will cause drama's with fish and plants, my deaths were caused by dead yabbies and another cause can be uneaten food on tank bottom but generally you will see a rise in Ammonia if this is a problem

As the fish are feeding well I dont think water quality is a problem and I agree with the other comments about your ph.
Feed could be your problem, what size pellets are you giving them??
Trout will try and get anything into their mouths and if the pellet size is too big they will often get it caught in their throat and die as a result.

skretting spectra SS 3mm

What about water quality? Can you see the bottom? Does the surface have a slick? Do the bubbles seem to stay longer than they used to?

A photo's worth a million answers =)

nup, water looks pretty good. there has been a bit of algae on the sides of the sump tank (where the SPs are), but I don't think there is at the moment.

Then I'd be leaning towards heavy metals too. Sometimes things just sort themselves out too.

Bore water has a lot more trace elements and the corry rainwater tank I'm with you gemmell, maybe more cycling needed