Sick Silvers

[saila]

Hi
I've got a problem with my silver perch. I've had them for about 18 months with no deaths. Recently they have started to die - about 2 -3/week. This has been happening for about the past 5 weeks. I have about 100 in a 2300L tank. I've checked water quality and it is fine. The perch that die have small red marks on them - some the size of a finger nail, others just a couple of small spots (looks a bit like a flat blood blister). I've done several 1/2 water changes and added 1ppt salt. This weekend I did a 3/4 water change, put any fish without spots on into a 10ppt salt bath for about an hour, and removed any fish with spots and salted the water to 1ppt. (I did use Brisbane water for the first couple of water changes as my water tank was disconnected - but the most recent change was rain water)

My questions are:
1. Any idea what is wrong with the fish? (or where can I get more info)
2. Anything else I should try?

Thanks for any advice (this will teach me for feeling smug!!)
Kathy

[GaryD]

Hi Kathy,

Can you take a photo of a dead fish with the red marks on it?

Once we see the photo, Crusty might be able to diagnose the problem for you. Apart from the odd example that I've seen, fish diseases are not my strong suit.

Gary

[Crusty]

Hi
I've got a problem with my silver perch. I've had them for about 18 months with no deaths. Recently they have started to die - about 2 -3/week. This has been happening for about the past 5 weeks. I have about 100 in a 2300L tank. I've checked water quality and it is fine. The perch that die have small red marks on them - some the size of a finger nail, others just a couple of small spots (looks a bit like a flat blood blister). I've done several 1/2 water changes and added 1ppt salt. This weekend I did a 3/4 water change, put any fish without spots on into a 10ppt salt bath for about an hour, and removed any fish with spots and salted the water to 1ppt. (I did use Brisbane water for the first couple of water changes as my water tank was disconnected - but the most recent change was rain water)

My questions are:
1. Any idea what is wrong with the fish? (or where can I get more info)
2. Anything else I should try?

Thanks for any advice (this will teach me for feeling smug!!)
Kathy

Hi Kathy.

Does not sound so good. When you say you checked the water quality, what did you check and what were the results. Two things that I would like to see is TDS (Total dissolved solids) and dissolved oxygen. Though these may not be available, the others Nitrogen, pH etc will be handy.

Two things come to mind, Anchor worm infection or (a better guess) Red Spot Disease, common in low pH and high organic load (both common in aquaponics). There is no successful treatment for the red spot but you can use 10g/L salt for 1 hour, then 5g/L indefinitely, lower the stocking density and transfer all the fish to a clean tank (chlorinate the old tank). The treatment for anchor worm is similar 10g/L salt dip for 1 hour repeated daily.

Add: I would slow down on the water changes unless you are trying to dilute a water quality issue. These water changes quickly mess with the water chemistry and will lead to other issues. Take a breath and take your time. Brisbane water as you may know is treated with Chloramine which is a more stable form of chlorine and is made by combining ammonia and chlorine. One mistake easily made with chloramine is the use of dechlorinators, they will separate the chlorine and leave the ammonia. Just and FYI, you can treat chloramine with sodium thiosulphate (used in photography - comes in crystals) as you would use it to treat chlorine, however you will need to apply 7 times the amount. Using the rain water may have sudden pH issues, so it may need to be buffered before use...

Good luck
Paul V

[saila]

Hi
I've attached photos (I hope!). Crusty - I checked ammonia (0); nitrite (0); nitrate (0) and PH (I can't remember - but it wasn't alarming - normally about 6.6 - 6.8.

If it is red spot - is there anything I should be doing for the remaining fish?
What causes red spot?
Are the fish ok to eat?
Thanks
Kathy

[Crusty]

Hi
I've attached photos (I hope!). Crusty - I checked ammonia (0); nitrite (0); nitrate (0) and PH (I can't remember - but it wasn't alarming - normally about 6.6 - 6.8.

If it is red spot - is there anything I should be doing for the remaining fish?
What causes red spot?
Are the fish ok to eat?
Thanks
Kathy

Hi Kathy.

That looks much like Saprolegniosis a fungal disease common with falling temperatures. These will cause secondary issues in your fish. Always associated with high organic load and ecto parasites. How is your filtration set up?

Take a read up on two things Epizootic Ulcerative Syndrome (red spot or EUS) and Saprolegniosis. These should lead you in the right direction. Please let us know how you go.

Oh and best to stop feeding until your water cleans up.

[saila]

Thanks for the info. At present I don't have filtration other than thru multiple grow beds (3x 500L and 2 bathtubs- all with clay balls and planted with a variety of veg) - I'll read thru this site and try to work out how to add additional filtration. Thanks again for the prompt advice.
Kathy

[arachdog]

Thanks for the info. At present I don't have filtration other than thru multiple grow beds (3x 500L and 2 bathtubs- all with clay balls and planted with a variety of veg) - I'll read thru this site and try to work out how to add additional filtration. Thanks again for the prompt advice.
Kathy

In that case I suggest the first thing you do is completely strip the clay balls from your growbeds and clean out all the **** that will have accumilated! Since all your other tests came back good, I suggest low DO from the decaying organic matter in your growbeds is very likely causing your problems.

[arachdog]

In that case I suggest the first thing you do is completely strip the clay balls from your growbeds and clean out all the **** that will have accumilated! Since all your other tests came back good, I suggest low DO from the decaying organic matter in your growbeds is very likely causing your problems.

Actually sorry that's poor advice, its not that simple. your going to have to do it in stages, since you don't have any other bio-filtration. Also I'm sure your not keen to pull up whatever crops you have going. But its a sticky situation and it looks like you might have to make a choice between the hydro crop or the fish. Meanwhile try and add some more aeration in any way you can.

[fishfood]

I would salt to 3 ppt and pump continusuly for 48 hrs removing the syphen or stand pipes [just continuous flow through the beds ]
if your water changes have removed the salt thats 8 kg you need in one go
In my book a bath in salt for 1 hr wont do much
Ho and plenty of air

[Crusty]

I would caution against changing the salinity of your system at this point as you run a serious risk of "stalling" your bio filtration while the bacteria acclimatise to the change. Keep in mind, regardless of aeration, the increase of salinity will reduce the amount of dissolved oxygen available in a system that may well be in poor supply already due to high organic load. It may be best not to disturb the grow beds while the fish are still in contact. The fish are best moved out, into fresh clean water and treated from there. Anything done to the system as it currently stands, runs a very high risk of killing the fish outright. Then work on flushing the grow beds and getting them back up to standard.