Backyard Aquaponics
A place to discuss aquaponics

Can anyone offer some suggestions as to why my fish are dying and advice on how to stop it?

BYAP system installed around 2 May.

4 GBs Planted up with seeds & small seedlings.
2000L FT, 1000L sump.
There was relatively little light until 2 weeks ago when we replaced more dark green roofing with clear laserlite.

5 gold fish in early on. 100 trout introduced 16 May. Total 5 trout have died over the past 7 days 1 or two at a time. Due to a spot of misreading they were getting grossly too little food until a week or two ago. Now getting more.

Last numbers taken on 13 June:
pH: 7.5
NH3: 1mg/L
Nitrite: 5
Nitrate: 20
Temp: 11C

I'll look through the problems discussions for answers but being at the bottom end of my learning curve any advice to speed things along will be greatly appreciated.

Still no new photos of the set up to post, sorry. I've not had many chances to be onsite myself recently and always forget to take camera.

Also, how much food should I be giving them now, given the age of the system and current parameters?

some of my trout are around 120grams
feeding 1.5% (of body weight) for 150 or so, about 270 grams/day...
About 1.8 grams each fish per day

When you say you were grossly underfeeding, how much are you talking about?

How much are you feeding at present? (exactly)

It is important to increase feeding slowly to allow the colony of bacteria to build and convert ammonia. This may take longer during cold weather.

Are there any signs in regards to fish behaviour eg flashing, gasping, not feeding etc.
Any damage to their little bodies?

Went from 2 teaspoons/day to around 6/day two weeks ago ( !!!).

I don't think there was any damage, but will find out if any was noticed. Sometimes one or two would look sickly (sluggish, swimming on side) the day before a fatality or two. Tends to be smaller ones dying.

Should we grind the pellets super fine to give the smaller ones more of a chance?

Do you have lots of air running in the system. And are you salting.

2 aerators. pump runs once per hour. not salting

nothing like a crisis to make you start learning. Looking at a few threads i've seen a few target values, incl. 1ppt salt and 3ppt. So for a start I'll chuck in 1ppt (ok??).

You want plain salt. Many people use pool salt. Avoid Iodized salt and table salt since it has anti-caking agents. Be sure to dissolve salt before chucking it in.
1ppt of salt would help protect against high nitrite for the short term. If it seems that the fish have an illness or parasite, bumping directly from 0 right up to 3 ppt of salt might be more effective for that. Most plants survive 3 ppt with the possible exception of strawberries and a few other really sensitive types (My strawberries seem to have survive 3 ppt fine though.)

Overfeeding or suddenly upping the feed amount with a new system can cause all sorts of problems. Ya want your ammonia and Nitrite to stay below 1 if possible. I know my catfish respond to stress or poor water quality by getting skin infections that can kill if the water quality and stress are not improved greatly. Anyway, suddenly going from 2 spoons of feed up to 6 essentially tripled the feed. Since I am seeing ammonia and nitrite readings, this indicates that the system was not cycled up to this load and you are having spikes. Reduce the feed a bit till the ammonia reading is 0 and the nitrite reading starts to come down considerably. 1 ppt of salt will help the fish weather the nitrite a bit better. Once your readings are back to normal, up the feed a little at a time while keeping an eye on water quality. (Don't jump from a teaspoon to 6 in one day. Say go from a teaspoon of food one day to perhaps 2 the next couple days to 3 for a couple days and so on until you have reached the amount of food appropriate for the fish/stage or you see your water quality start to spike again.) If the water quality spikes again. You need to pause at that feed level and ride out cycling up to that level. This all takes longer with cooler water/weather.

Thanks TCL, really appreciate it

Nitrite of 5 is your problem.

yeah , I second that

Nitrite of FIVE ?!

water change

Latest readings below. I’ve been neglecting the fish due to increase in work (I don’t live at same location as fish). Obviously have to make time and learn more - quickly.

100 trout introduced 16th May

Date pH Amm Nitrate Nitrite Temp (C)
16/05 7.0 0.25 0 0 12.5
23/05 7.6 1 0 0 12.5
01/06 7.6 3 0 0 15.0
06/06 7.6 2 0.5 5 12.0
13/06 7.5 1 5 20 11.0
20/06 7.6 1 2 40 11.0

No deaths for 1 or 2 days

those numbers are cluttered. how can i tab between numbers within message body? I tried typing it in Word then pasting but tabs disappeared.