Not much room & form trumps function! Salad tonight anyway!

Dangerous Dave

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The silver perch bottarga worked OK... at least I think so, having never eaten bottarga before. Tastes like anchovy. No suprise I suppose - it's basically dried caviar. Very salty and a bit crumbly... I grated it over some green beans and it tasted pretty good. They're tiny though... that's a bread and butter plate they're on.

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The growbeds are going gangbusters. Just did a big harvest and will be planting in the available spaces. My latest experiments are with microgreens - have done radish and asian salad greens and now trying Chinese cabbage. The seeds sprout in a week or two... easy to pull out and taste great in salads. I thought it might help with my high nitrates but have realised that the sprouts are probably just using the seeds for all they need when they're that small.

Last week I split my stingless native bee hive. The original is in the garden just out of shot to the left of the picture. The new hive has pride of place high above the aquaponics... with luck, I can harvest some sugarbag next October. The native bee hive man says he thinks the insect hotel just behind the top of the broad beans might be a bit of a gimmick... has been there a couple of months now and no obvious insects resident as yet.

Dangerous Dave

Nearly a year since last post. All going smoothly. Spring has arrived in the Northern Rivers - watercress, flowers, herbs, chilli bushes and leafy greens going strong still... and tomatoes have started fruiting.

Will be needing to eat a few of my fish in next couple of weeks. I have 25 plate sized fish... close to theoretical capacity in my system. First to go will be a couple of silver perch and then my biggest murray cod (will post on the MC in another thread).

In preparation for harvesting, I did a stock take - including my sump tank for the first time ever. Have long been unsure what survives in there... access is difficult.

Turns out I have 4 surviving eel tailed catfish (tandanus tandanus)... so none lost in last couple of years. They don't grow as fast as jade perch, or even silver perch. One is a bit smaller than the rest... others are about 40 cm and 600 g. I believe they're great eating. But I've come to enjoy the way they get excited around food time... they could easily be hand fed but I don't because of the extreme pain if spiked by their dorsal spine. So my strategy of not getting friendly with my fish, so I feel OK about eating them, has failed! They'll go back in the sump tank and live to an old age.

Dangerous Dave

Needing some help please.

Have been away a couple of weeks. Fish were fed for much of the first week but probably pretty hungry by the time I got back last night. But system looks good and all but one fish look OK and are eating today.

One silver perch was swimming on its side or upside down when I got home. And upside down on bottom of tank half an hour later. I dispatched it. It looked healthy to my inexpert eye - apart from some sort of lesion on its side. Full of roe and plump.

When I first saw it in the tank in dim light, I thought that one of the bigger murray cod had got hungry and had a go at it. But it doesn't look like that on close up. Looks more like an ulcer.

I plan to salt my tank - just in case.

Photos below.

Grateful for any thoughts.

Dangerous Dave

No further deaths. But fish don't seem as hungry as usual... maybe I'm imagining it... hard to tell!

Still hoping for some thoughts on my picture above. But now also seeking advice about salinity.

I added salt to raise salinity by 1 ppt. I guesstimated I would end up with a salinity of about 2 ppt. But I just measured with a hydrometer and got 5 ppt.

The hydrometer was cheap with no instructions. I wasn't sure if I should ignore the capillary effect... if I do, my salinity is 3 ppt - and I'm happy with that for now. I've persuaded myself it's 3 by checking my tap water and the hydrometer (with capillary effect) says 2 ppt (I think should be 0.4 at the most).

Have just re-read various posts on here about salinity and how to measure. I've previously tried with an EC meter. But I got confusing results and not sure if I was measuring just salt or if reading was compromised by things like magnesium, potassium and calcium added when bringing up the pH. Have also tried with a refractometer - but they're designed for salt water tanks so the reading is right at the bottom of the scale and my eyes aren't good enough to get anything even close to accurate.

Having typed all that, I've just realised I've been missing the obvious - if it's 5 ppt now, it was about 4 ppt before I added the salt - and system was doing well. Nevertheless, would value some advice on whether anyone has found a refractometer with a scale suitable for aquaponics. And if my logic is OK in regards to ignoring the capillary effect on the hydrometer.

rininger85

Tagging in because this is the first I've seen your thread... Awesome little system! It seems you've been packing it full of produce and maximizing every usable space.

As for measuring the salinity, I believe you want to ignore the capillary effect and measure at the bottom. Normally measuring tools are calibrated that you measure to the bottom of the meniscus for an accurate reading.

Nhibbo

Hi D'Dave. I use a digital salinity/Temp meter from eBay that I've been very happy with. It cost around $65 delivered to Melbourne. (I tried to download a photo of it but I am hopeless at that). Very accurate meter.
The meter is a TekcoPlus SMTK-49 Water Quality meter. I'm sure you can find one on eBay. (I just had a quick look but the one I spotted just now does not ship to OZ, but I'm sure you can find another supplier without much trouble)
Good luck.

Dangerous Dave

Thanks Nhibbo.

Pretty sure that's the same meter I was using, without any confidence, a year or so back. I'll dig it out of my shed tomorrow and put some new batteries in it.

But can you clarify if it just measures salinity (sodium chloride) or if the other dissolved solids in my water cloud the picture? (I add things like Epsom salts, calcium carbonate and potassium hydroxide).

And thanks also to you Rob. For the feedback on my system and reassurance about the meniscus. Means I'm at about 3 ppt.

Nhibbo

Hi D'Dave.
I just reread the operating instructions. They state that it measures salinity (+ - 0.1%) (NaCl). It also states 'compensated' without explaining what compensation is done. I assume it would measure total dissolved salts (someone else might be able to explain if/how NaCl can be separated/compensated for/from total salts).
When adding salt to my systems, i have done the calculations and either added pool salt or seawater (beach is nearby) and used the meter to check my calculations as a backup. I have found it to be very accurate.
I also add Epsom salts to my tanks. To my way of thinking, total dissolved salts is what is important here and will provide osmotic protection for the fish (providing the bulk of the salinity is NaCl).

Dangerous Dave

That makes good sense. Thanks Nhibbo.

Nhibbo

Oh, I just read your question asking if it measures TDS. No, it measures salinity.

rininger85

Compensation I believe is referring to temperature compensation... I forgot the exact reasoning behind it but apparently temp makes a difference.

Dangerous Dave

Just saw a post on another thread... viewtopic.php?f=2&t=29216&start=15#p560590

Wondering if the silver perch in my Oct 15 post also had Saprolegnia parasitica fungus. I couldn't see any fungus on its gills... or around the lesion. But I've seen markings similar to the one in Loser's thread on my fish before. I can't recall if this was in early winter, when it seems to be more of a problem. And I've had no multiple fish deaths - AS YET :think:

Loser

Hi Dave, your thread just popped up in my saprolegnia search...
The pic you've put further up looks very similar to what I have seen on a couple of my deceased SP.
Like yours, I couldn't find any fungus on the gills. Some of their gills seem whiter than others though. Doesn't look like a fungus, just looks like the complexion of the gill is a pale colour as opposed to the reddish colour gills normally seem to be.
Does seem weird to me that Sapro is getting to my SP, as water temps are between 27C and 29C at the moment.

Hopefully a solution can be found.

Dangerous Dave

Thanks Loser.

Definitely no problems with cold water up here in sub-tropical Northern NSW. And I salted the tank after I saw that fish a few weeks ago. But, as best I could tell, the salinity was 2 ppt in the first place.

Anyway, have had no further deaths in that tank. I harvested two SP and two Murray cod last week and they all looked very healthy - and tasted pretty good too! But I didn't examine the gills or look for spots quite as closely as I will next time.

I've recently added about 10 small jade perch. The remaining SP and the new JP are all eating well and look fine from a distance. Will keep my fingers crossed.

I'll keep an eye on the other thread and will chime in if I have any bright ideas.

boss

Sorry about the one fish loss. Glad you got past it okay. I'll need to go look how to do a salinity test again. I have a the refractometer, but I didn't know about taking a sample from near the bottom. I love the way we learn from each other here. Thanks Dangerous Dave.

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