Backyard Aquaponics
A place to discuss aquaponics

Our system finallly cycled and we added approimately 55 Rainbow Trout on Saturday 27th March. Our water readings appear to be good, but we have so far lost 12 fish, a fish every day, sometimes 3 at a time.

Fingerlings on average 120mm.

They ate on the day we brought them home, but have not really been that interested since then. Some have been interested yesterday and today, but not overly.

They appear to be swimming around actively.

Any help would be appreciated as we don't want to lose them all.

How big is your system and type, do you have an air supply, what temp is your water etc.

Same as above Tea20 questions, plus if they did not eat, did you remove the uneaten food?? Uneaten food at the bottom of the tank will very quickly affect trout health...

IMO, never feed the fishes the first day you put them in the tank... let them settle down for a day at least or two days...
Sometimes it might seem they "attacking" the food but once below the water surface, they might spit it back out... then the food will be left uneaten at the bottom of the tank... and the horror starts...

How much did you feed and what is the weight of the fishes??

More info needed please...

pH, water temp, tank & growbed size, pump intervals, pellet size, feed amount...

Welcome aboard, Gaz,

Rotten food or dead fish=ammonia. Also an increase in fish load may cause a spike if the system was not up to that rate. So, test ammonia and nitrites and let us know.

New fish =stress. Give them some salt for at least a week, especially if they are dying. 3ppt for now. NOT table salt as it has additives like iodine and anti-caking agents. Pick up some from a aquarium fish supply store or (cheapest alternative) get pool salt from your local hardware or whatever. My local store has 40lbs (18kg) for under $5.

+1 on not feeding for a day or so after arrival, but that is water over the dam.

Do make sure that the fish either eat all the food in about five or ten minutes or that it gets quickly sucked up and moved to a growbed where you have a strainer to collect it before it piles up and rots. Later your worms can handle some excess food, but right now your ecosystem is unstable and immature.

Good luck!

Tank is 900 lrs
maximus kit

water levels have been consistent

have not taken levels the last two days, but prior to that
ph nitrite nitrate ammonia
7 .25-.5 10 0-.25

feed size is just a pellet at a time, not handfuls, to see if they eat

we have good air supply, air rocks, so no issue with airation

water temp between 19 - 22

In Melbourne

I'm assuming the "10" reading is nitrate... not nitrite...

The trace readings for ammonia and nitrite probably reflect any uneaten feed and dead fish before they were removed...

Water temps of 22 are toward the upper limits for trout... especially fingerlings.... pump as much air as you can into the tank

maybe get out the test kit and test again. if you have fish dying the idea is to take current tests as results change very rapidly. 55 trout in a new (even though it is cycled) 900 litre system is really pushing it.

If that reading of 10 is nitrite, thats your problem. Follow all the advice above. And monya is very correct, I stocked that many trout in a 5000 litre system for the first year.

AND they are HUUUUGE trout for a new system!!!! Whoever told you that it was ok for fish that size in a new system should be shot.

Yep, missed the post regarding the size.... even if half that size... 55 trout in 900L is pushing it even with a mature system...

About half that number is what we'd recommend...

I know that other people have stocked that many in similar kits... but usually in a mature system... and usually with water quality problems...

If you got your kit from a local Geelong supplier... I'd suggest you review his thread... even though experienced, he struggled... and lost fish...

Don't feed for two days... retest now, and then tomorrow... and please post results...

Thankfully... the "Maximus" has about 1400L of growbed volume... when mature it should cope... but only just...

You could always expand it with two additional beds later as the fish grow...

Am I correct? 900 litre fish tank 55 rainbow trout = way overstocked IMHO

To help your suviving fish you might want to do regular water changes to help lower the ammonia levels and only feed very lightly every few days. with that many fish in such a small system you will strugle, I have 3 fish(150mm) in a 700Ltr system even after I cycled it

yes the 10 was nitrate. apologies

what about adding salt? someone told us to do this and also someone who responded mentioned it as well.

we will stop feeding and I will take more readings.

water readings just taken
030410

ph 7.2
nitrite .25
nitrate 10
ammonia 0-.25

Water temp 19


we are sure that we heard the ratio of 1 fish per 10 litres of water from the video. we chose 50 fish because the amount of water cycles between 500 - 900 ltrs.

2 - 585 ltrs grow beds
1 - 200 ltr grow bed
925 ltr water

fingerling size average 100-120mm
weight not sure, but similar size as middle finger

yes we did get it from supplier in Geelong, which caused us no ends of problems

Salt will help to destress the fish, it also reduce the effects of nitrite posioning. Since your nitrites are currently 0, it's not a big deal, however, I think that with that many big fish, nitrites will soon be a problem. Add 1.5kg of pool salt.