Backyard Aquaponics
A place to discuss aquaponics

Or maybe he could measure some kind of general hardness or something? Maybe he could also check for salinity? Because the fish food if made from sea-products may be salty and salt may accumulate over time if the plants never use it.

Fish too may lose water (by the same osmosis) when the hardness/concentration of dissolved stuff is high outside their bodies. So this also could explain fish deaths.

Well, the goldfish actually are supposed to live in hard water, so it may explain them surviving.

Gokul, the sort of "dissolved salts" you quote are references from hydroponic methods... usually as a result of "salts" locking up or precipitating out due to combinations of pH and temperature....

Not applicable in an AP system.... that produces nitrates directly as part of the nitrification process... and trace elements in soluble "ionic" form through breakdown in the growbeds...

Unless they've been dumping large amounts of Calcium Carbonate (not mentioned, but possible by the pH reading) or chelated iron (seemingly not so by the plant descriptions).... or some other sort of "fertilisers" or substances...

Then I think the answer lies more in a combination of "flood and drain", aeration, decomposing food, anaerobic zones and temperature issues....

Think the best idea is to dump and flush the system and start again..... testing regularly from the start....

See mention of testing by "swizzle sticks"....... not sure what is meant by these... but I would seriously suggest getting a reliable, tested and proven kit... like the Master Test Kit.

jimmy some random thoughts...................

dumb question, but the growbeds get good sunlight?

forget about the swizzle stick tests. IMO if you cant be certain of the results then you may as well ot test. Get a good quality master test kit. Joel sells them cheap.

I find it VERY strange that a system 1 year old has ANY measureable ammonia or nitrites.

At this stage i'd bite the bullet, use the 1500L to water some dirt plants, and re-fill the system with virgin water. This will remove the high dissolved salts / possible toxins from the equation.

turn the system OFF, drain the water, remove the fish, re-fill the tank, DELCHLORINATE the tank, turn the system back on.

Forget about the bass i've had a couple in a heated aquarium and their growth rates are terrible from my experience.

Re-stock the system with 30 trout, hit the feed HARD while monitoring ammonia and nitrite and if detectable amounts show then stop feeding or wind it right back until they dissapear. repeat.

You've still got time to get trout to plate size if you get them at say 8+ inch

Steve

I did buy a thermometer / hydrometer that measures density (which is supposed to give a broad indication of TDS).

Otherwise, I guess I can take a sample of water and bring it into uni here to run an EC test.

So in any case it looks like Dad may need to invest another 1500L of water, and about $300-400 worth of hydroton.

My first look at the system pictures and I said uh oh, I hope that galvanized tank and bed are coated or lined with a fish safe coating/liner. The zinc in the galvanizing can become toxic to fish and if there is any copper getting into the water, the zinc can make the copper more toxic to the fish. This of course is a slow leaching process that gets faster at lower pH. Even people can become sick by eating/drinking acidic foods that are prepared/stored in galvanized containers.

Then after reading your story, I realize that most of the fish deaths have been due to cycling mishaps and other HSM situations that happed due to temperatures, pumping/lack of it, feeding, lack of testing, etc. It seems that only the most recent deaths are unexplained. If the water can be found for it, I agree that a water change and starting fresh like Steve says is probably your best bet. If deaths start happening again and testing shows it not to be Ammonia/Nitrite problems, then I would fear the galvanizing got em.

I agree with those that are pointing to a possible issue with your test strips. They are rarely very accurate. The master test kit is probably a good idea using the drops may seem like a pain but getting bogus test results from easy strips doesn't help you much.

Jimmy... EC and TDS aren't values that really need to be measured, or give any reliable indication of water "quality" in AP systems... they're hydroponic measurements...

In AP we need to measure temperature, ammonia, nitrites, and nitrates...... very occassionly we might measure salinity if we're salting for fish health...

Think recirculating tank aquaculture technology or aquarium keeping....

Buy a Master Test Kit and a thermometer....

Okay, so Dad's to-do list is now:
- find thermometer (he has one)
- buy proper test kits for NO3 & NO2 (already have proper stuff for pH & NH3)
- buy hydroton
- test water one last time
- take goldfish out & store in bucket
- empty growbed & wash thoroughly with fresh water
- drain tank & refill (dechlorination not necessary as it's 100% rainwater)
- re-stock with original 9 goldfish
- fill growbeds with hydroton
- correct the flood & drain cycle and water levels
- set up a schedule for measuring & recording water quality
- wait for system to cycle up
- stock with small number of fingerlings

By the time Dad is ready to do all of the above, I expect we'll have missed the cool weather required for trout. Better to think in terms of silver perch I think.

Update on this system...

Dad has disassembled the entire thing and given it to me as a Christmas present

I have thoroughly scrubbed the growbed and the insides of the pipes (fun job.... not!). The fish tank will be fitted with a new liner as it is now an in-ground fish tank (aka pond).

A thought struck me as I was shopping for pipe fittings --- glue. I have read on the other parts of the forum that blue PVC cement is okay, but I wonder why only one brand of silicon glue is labelled "aquarium safe"? Makes me think that the choice of glue in this closed-loop system could be critical.

Notwithstanding all of the errors in management that account for a large number of fish losses in Dad's setup, I do wonder if we also produced a toxic combination of glues when setting up that system that accounts for both the poor plant growth and the difficulty in keeping fish alive. From memory, for all PVC joins we used a red cement (not even thinking about whether it's poisonous), and some unknown non-clear silicon sealant to fit the drain to the GB. I cannot remember if we flushed the system or just filled it up... Yikes, we could have been cycling nasty chemicals from the word "go"...

Anyway, as a precaution I've bought some aquarium-safe clear silicon sealant and cut out any fittings that had either type of glue (including ripping the drain out of the growbed). I will also flush the new system before adding fish!

hey Jimmy, good score

Make sure the silicon cures for a few days too. Have fun with it.

Some of us use silicone instead of pvc glue, and its remoeveable later as well.

Does silicon form a satisfactory seal on the pressurised parts of the system? The pump I'm using is a fairly large pond pump but I think it wouldn't deliver massive pressure...

I glue all pump delivery lines (well I do now anyway).... but silicone is fine for return lines...

Anything less than 8 metre of head does fine without glue in my experience.