Backyard Aquaponics
A place to discuss aquaponics

Hi, I am new to the forum but have been running a system since september 2006. I have a 2000 ltr fish tank which is stocked with 100 Silver Perch, of various size ranging from 100g - 250g.

The water from this tank is pumped to 6 x 600 ltr grow beds which are filled with 10mm gravel. It's a flood drain system with water following back to the fish tank via a main drain. The system is housed in a enviro tunnel.

The system from start up until November 2007 operated as expected, as described by Joel's manual. In November however there was a sudden deterioration in water quality that I have been unable to correct todate despite partial and complete water changes. The water become dark green in less than a week after a complete water change.

The fish on a whole seem healthy, hungery and active but at irregular intervals one or two of the medium or smaller fish will start to swimming to the surface and later swim upside down. At this stage they do try to right themselves but enevitably die. There has been evidence of some reddish marks on some of these fish.

Another factor that may be questionable is a change in feed. They were being fed 2mm Juvenile pellets but around November this was changed to 4mm grower pellets for native fish.

The growing beds have been very productive but at the moment are generally producing herbs that are not as prolic and healthy as last summer.

If anyone could help me out with any advice, I would greatly appreciate it.

Chris

What are your readings on ph, temps, etc. Has your aireation method changed?
Listed ingredients in the new feed compared to the old feed?
The alge bloom causing a decrease in O2 content perhaps, but whats causing the sudden algea bloom? The new feed? Since your problem seems to have started with that, would be my guess. Add more air if you can at least untill its sorted out.

Under etc above, are your total ammonia and nitrite levels still OK? I found the Sick Fish page on the net quite useful when I had health problem with some of my silver perch, despite the fact it is focussed on ornamentals. http://www.angelfire.com/blues/fish_problems/main.html
The photos under fish diseases show some symptoms of red streaks. Having said that I agree that additional aeration could be a good immediate strategy.

Is your fish tank covered Chris (welcome to the forum) - algae loves on light and feeds on O2, thus depleting the water content.

A test kit is a very good aid in helping to fault find on a system...have oyu had any problems with the wet weather...abundance of rain getting into the system to upset the balance

Nice sized system you have there and if it has been running for over 15 months then it would be mature and suggests that something abnormal recently has occurred to upset it

Hi Chris and welcome to the forum.

You say the system is housed in a enviro tunnel... does this include the fish tank?

Two things will help us help you.... pH,ammonia, nitrite and nitrate readings are an obsolute must have.... water temperate and breakdon of the "new" feed and differences from the old feed might help as well.

As well as increasing the size of the feed pellets did you also increase the amount and/or frequency of your feeding Chris?

Edited :

In the mean time Chris I'd stop feeding for a day or two.... stir the tank and double the pump cycles if you can to get rid of any excess uneaten food and breakup the algae.... are you on a timer??

Add an aerator (or two) if you can... if not pumping more often will help... and or do another water change... maybe 30% min.

Did you happen to see the colour of the gills on the dead fish?

Yep - Chris we need those readings and some details about your method/s of aeration before we go any further. There are many possibilities - one possbility being that your pH has gotten so low that the biofilter has crashed.

Just another side question though - while awaiting those details, when you changed the water, where did the new water come from? If from the tap - did you neutralise it. A 100% water change is something that would never be recommended BTW.

Yup, need readings. I'm suspicious of low pH plus pH fluctuations due to algae. Chris, try getting a couple pH readings for us, say early morning and late afternoon.

Think that where the three of us are heading.... pH... the rest are affects that have arisen or been exacerbated by the pH

Chris must not be too concerned or he'd be back here checking what the replies are. Looks like we are more worried than him .

her

him, her - whatever. I'm not sexist

just like sex!:wink:

to be fair to chris, most of you are rabid posters it usually takes a month to generate as many replys on most forums.

Um, horray!

Agreed, most of us have not had our shots either. mmm time to have one I guess, its after 12.

Wow, I'm blown away by the responses. thanks heaps.

The fish tank is undercover and I have not intentially increase the amount of food, although I did suspect they got an over does when a friend looked after the place for a few days.

Will do my best to get ph reading twice today but I only have test strips not a wizz bang kit. Will send a report this evening. Thanks once again.

Chris