Before, I had a 6 foot, 2-inch diameter carbon filter.  I had this directly inline with the pressure compensating drippers to fill the tanks, which had siphon overflow systems to keep the levels constant.  The problem was that the water was flowing through the filter uncomfortably fast.  I didn't have much excess capacity.  As the carbon absorbed chlorine and chloramine, the safety buffer came down.  After 5-6 months, I got the first traces of chloramine bleed through.  That wasn't bad for a few dollars worth of carbon!

I'd done some research since setting the system up and apparently there are some sort of guidelines for how long you need the water with chloramine to be in contact with the carbon to ensure that its all but gone.  Apparently about 15 minutes seems to be the good rule of thumb.  My old system, while it had very high grade carbon, only had a contact time of less than 1 minute.  Not good.

So, what I did instead was use the carbon filter on a slow trickle flow to fill a tank, then use a pressure pump and bladder tank to provide pressurized dechlorinated water where needed.

Instead of using a solenoid to turn the filter on/off, the system is always on now and has 60-70psi to work with.  Each location has its own solenoid, pressure regulator, non-return valve etc.  No solvents or PVC come into contact with drinking water.  The bulk of the equipment is outside now.  Its almost all FDA grade LLPDE pipe and fittings etc.  (The only thing that isn't is the original inline filter).

With a few other tweaks, this all works out now such that the water now has closer to 8 minutes of contact with the carbon.  I've checked the chloramine/chlorine levels with a Hach low level kit and its comeing out to as close to zero ppm as I can measure.

Everything else is unchanged.  My systems still change 10%-20% of their water every day, automatically, without human intervention. 30 (exactly!) tanks with no manual water changes is priceless.

However, trouble has been brewing.  First of all, our tap water has a very low conductivity/tds.  My fish essentially live in pure dechlorinated tap water.  I've had penguin biowheel filter motors jam for 4-6 weeks without me noticing, and no apparent ammonia buildup.  (I have ammonia alerts in every tank).

But, the downside is that the tds of the water in the tanks is very low.  For guppies, it is Very Low(TM).  I'm regularly mesuring it at 30-40ppm tds in the tanks.  I've read that guppies don't cope well with it below 110-120ppm tds or so.  I'm starting to agree.  I'm seeing a frighning incidence of dropsy-like symptoms.  I tried adding salt to increase the tds to about 200ppm, for a few months and new cases of dropsy symptoms pretty much stopped.  I let it drop down to 100ppm-ish, with no obvious effects.  Since then its crept down even more and the bloating has started again.    And this time, on males too.  Uh oh.

Back to the drawing board on that.  I think I'm going to mess with RO to see if the "waste" water is more suitable.  (I'll keep the product water for drinking, but it seems amusing to think of the pure filtered water as "waste").  I'm not sure if this is going to have enough of an effect with such pure municipal tap water.

But this problem isn't new.  The low tds water has been there for 8+ months now.  I'll deal with it somehow.

But then things got wierd over the last 1-2 weeks.

I moved a step ladder and found about 10 of my prized japan blue/double swords on the carpet, all crispy.  What the...??

A few days later, three of my eight bloodfin tetras jumped out.  I did a headcount and discovered that my 5 initial diamond tetras are now 11 diamond tetras.  So obviously somebody is happy with the tetra tank..

And a few days ago, the grandmother of all my japan blue/double swords jumped out!  She's the original sole survivor of the original set that repopulated the strain where I'd lost all the males.  What the ...?!?!?!!!?!

And this last week, my Pingu's have been dying off by the cupload.  Literally. 5 to 10 per day!  Admittedly, they've been acting wierd for 2 weeks now.  Usually they're frantic at feeding time, and they suddenly all went quiet.

I've rechecked all the water chemistry and I can't for the life of me see anything obvious.

I initially thought the camallanus worms might have been back, but I can't see any trace of them anywhere.  Not even in the corpses.

I'm completely stumped.  There are no obvious signs of illness.  One day the fish are swiming around with nothing obviously wrong, the next they're belly-up on the ground.  I know this is sudden because I noticed that one of my original 6 pingus was still around and appeared to be fine - she was the only one with  a particular obvious identifying feature.  The very next day she was dead.  I couldn't believe it.  The very fish I'd noticed the night before was dead the next day.  While I'm not 100% certain, I think that was a 12 hour kill. That's not good.  :-(

What is really strange is that the strange things appear to be confined to particular species or strains.  eg: why only the bloodfins, in a whole tank with 5 other tetra types? - especially when the others are breeding against the odds?!?  Why are just the jap blue/swords jumping?  Why are just the pingus dying so fast?

Things have been alarming enough that I'm starting to seriously consider taking some newborn fry from each of the important tanks and set up a backup colony elsewhere, just in case.  One of my neighbors has agreed to take some of the japan blue/double-swords as a backup colony.

The one and only thing that I can think of is some accidental ant poison contamination. Deltamethrin is seriously toxic to fish and I'm wondering if somehow the dust got into some of the tanks somehow.  This possibility is disturbing because the only way this could happen is if I had dust on my hands and carried it with me for some time...