Backyard Aquaponics
A place to discuss aquaponics

One question: Do you prune your tomatoes? I remember when my father used to grow tomatoes commercially he used to go through the greenhouses on a regular basis cutting back the plants; which increased the fruit yield; while reducing the amount of fertilizer required

At the moment I've got some cherry tomato seeds, I'm reluctant to plant the bigger varieties since I know they're very hungry buggers.

Oh well with only 0.25 ammonia; not nitrites and definitely no nitrates, it's going to be a while before my plants get anything like a good feed; which is why I've only planted a few..

Well, there's more than one way to add ammonia; but when it comes to eating the fish...a little too "recycling natures bounty" for my comfort

For your tomatoes, prune out the side shoots and let the main shoot grow to increase the harvest.

E2, our tomatoes get pruned back every week or two, then after you finish and turn around to stand back and admire your work... they bushes reach out and menace you again

They grow very fast. This morning's pick to give some to a friend who gave us some ibc's brought the tally up to 20kg picked since June.

System looking good eame0002..I hope your new hobby provides stress relieve ...sometimes its raises the stress levels too

Jaymie I heard that tomato cuttings will root and grow another plant in a AP system. I could see you now down the weekend market selling tomato plants
LB

I will vouch. I rooted 2 tomato cuttings in my system. They root quite easily.

E2, have read of this thread on tomato pruning, especially the info provided by Raimo
Tomato Pruning Hints

F&F, trying to lift about 100mm above water level - then feed it into a filter to save trying to scoop it out of my sunken sump tank.

Oh well I knew it had to happen sooner or later but I was hoping for later!

A couple of the silvers died in the first couple of days; they looked a little worse for wear when they arrived, due to a bag of food shifting I think (the rest of the silvers were fine), so I didn't count them as deaths.

but over the last few days I've lost two more silvers; both times they started flashing and then did the float on the surface trick

The rest of the silvers are eating fine and swimming around like small rockets, everything in the system is fine (ph a little high at 7.6); except for the ammonia which is at 0.25 (no nites yet). So I suspect they just didn't survive the travel/environment change and gave up the ghost. Still I'm taking these two personally.

I've had the fish a week now; so hopefully the rest have settled in. What sort of fatality rates have other people had?

To be honest I've told my partner that due to having a lot of theoretical knowledge; but no practical...that I'm allowing 50% over the growout period (not that I expect that many; but I'm covering myself with the "funding agency " )

If you're fish are flashing E2.... you might consider salting the system as a precaution....

Just about feel qualified enough to say ease off on the food. The fish respire ammo anyway, until the nitrite bacteria kick in, all u will be doing is adding to ur ammo levels. It will then take longer again for the baccy that converts nitrite to nitrate to kick in. At ur pH there is not a lot of room for ammo/error, if u get a couple warm days, could be in trouble. (Ammo toxicity is relevant to pH and temp, check out Steve's write up in the useful info section.)

or stop feeding them and do a water change?

All of the above. I'd say stop feeding for a few days, add 2-3ppt salt, and do a small water change. Try to keep the tank shaded or cooler if possible, and avoid stressing the fish.

As far as mortality rates, of the fish that made it into my tank alive after their horrible transport issues, I lost less than another 5% during the first week. From that point onward, I have lost one. Tilapia are pretty tough fish, though.

had a few thoughts about ammonia and would like opinions

My current ph is either 6.8 or 7.8 (depending on which test kit I use: strip or master kit, and I think I'll go for the master kit). My total ammonia is somewhere between 0.25 and 0.5 (damm shades of green, they're too close together)

My current water temperature is around 20 degrees C.

So using the magic equation (ok looking it up in a table and using a ph of that gives me ammonia of 0.025 (5% of 0.5) which is pretty safe.

My "pond" currently holds around 9 thousand litres, with room for 3 thousand more and changes very slowly. For instance when I first read the ph as 7.8, I decided that it should be 7.5, so I purchased some PH down (only 500 ml) and started slowly adding the damm stuff over a week.
End result ph still 7.8 (Ok can anyone say buffering and water volume, and should have realised). The same goes for temperature and ammonia; everything changes veeeeerrrrrrrryyyyyyyyyy slowly.

Despite the above I've added around 500 litres of fresh water, and a little salt. The 500 litres made no difference to ph or ammonia; but made me feel better

So given the above and given that my carbonate levels are pretty good (and didn't even blink when I added the ph down), I have nothing to worry about?

The clincher for me is that the fish are doing fine (they lie in wait in the pond and almost jump out when I appear carrying a container), except for one which is flashing and I intend to dip that one.

As an aside, if my Total Ammonia Nitrogen gets out of control, or the temperature of the water soars, and extra water doesn't help. Then I could lower the PH. I've read Epson Salts (magnesium sulphate) , is good for this (not going to buy any more expensive commercial stuff).

Has anyone done this? If so did it work well etc?

Your pH will naturally drop over time, and the bacteria will probably establish faster at the higher pH. Don't let your ammonia get any higher than it is, but I checked the charts, and agree that you should be OK at 0.25 - 0.5. Glad to hear you added salt. That buys you some safety.

If you need to decrease pH, there are several potential cheaper solutions. Add wood, filter the water through peat, increase aeration, or add plain (cheap) white vinegar. I would go for the vinegar. I have not used Epsom Salts (MgSO4), but doing a brief search showed its use to increase hardness or supplement Mg. I don't think you want that.

I would add vinegar slowly if you have to drop the pH.