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Re: KH & Discus

> I know some, like Paul Sears, have said that one's KH can actually be kept
> lower than the 3-4 generally advised without risk. I would like to know
> just how low I can keep our KH given our setup:

Your doing daily water changes what about daily testing? You can do it but
there's the associated risk of dropping too low. If you keep a close eye on
it you can do it. This is more a fish set up rather than a plant set up.
Quite a large number of folks have done Breeding at higher KH/GH's. I
believe you'll get better yields of fry out of a bare tank with no plants.
Then the issues of CO2 and KH don't matter nearly as much since the plants
needs are a non issue. But you want both so there's the trade off. It's
worth it to me personally though.
> 
> -- We moved our 135-gal tank with the plants (not fish) to a city with soft
> water one month ago. Old Plants and new tetras and corys doing very well.
> 
> -- We just got 8 discus and will be doing *daily* 20% water changes per our
> breeder's suggestion

You wish to breed them correct? I can totally assure you daily water changes
are NOT needed otherwise. That's total hogwash.


Another thing about that: You can do this daily water changes to *induce
breeding* but it doesn't have to be kept there all year long. Later you can
back off this workload(which is exactly what it becomes!) after you get some
spawn.

> The water changes in a planted tank are not so much
> aimed at removing waste to keep nitrates in check, but rather to prevent
> the buildup of "stunting" hormones or enzymes that some fish secrete in
> tanks that prevent them from reaching full adult size. That's the theory,
> at least.

Carbon will/should remove those. I certainly don't buy the stunting idea. I
have seen no evidence with anyone's fish that does more water changes over
someone who doesn't myself included. Feeding is more likely what's going on
there. Diet is more important than this issue ever could be. If you feed
like crazy you also will build up waste faster, not so much this stunting
enzyme/hormone. The waste from heavy feeding is likely what's at hand here.
I've seen Discus that get, if they are lucky, a weekly 20-30 % change. they
are full blown adult sized fish. Are bigger Discus better discus?
Not to judge, but to you? Is an inch smaller a cause for concern? Will it
affect spawn sizes or abilities? Rumors or fact?
 It seems like a rumor to me. A Big tank with less fish will help. 5-8 in a
135 should pose no problems. Food is the most important issue for just about
any fish breeding attempts. Are these wild or tank raised?
We got some heavies in the Discus world here and I can ask them about all of
this issue but it seems very unlikey.
I'll get back to you on that.

> -- We keep (and used to keep) our (pressurized) CO2 around 10 ppm. Our
> Barclaya gets holes if the CO2 is much higher; plant growth has been
> exellent in the past with this level when we kept angels; discus may be
> sensitive to high CO2; I've been using up some Flourish Excel, too.

I did well with Barclaya at higher CO2's. If your getting holes in the plant
it's not from the CO2. It's always easier for a plant to use CO2 over
Carbonic anhydrase enzyme for a carbon source. Algae as well. They only
produce it when CO2 is low(both (some) plants and algae). Algae are very
good at it obviously. Egeria/horwort/eel grass and others are good as well.
I think Barclaya can do this as well.

 Discus are NOT any more sensitive to CO2's than other fish I've had.

> 
> -- 4 x 96W PC lighting (2.8 watts/gal). Good substrate & water-column
> fertilization.
> 
> -- Tap GH is 41. Again, our discus breeder uses and suggests a growout GH
> of at least 150. We are keeping the GH at about 150 ppm with magnesium
> sulfate and calcium chloride.

Sounds good for plants and fish.
> 
> -- Tap KH is 24 ppm (1.3 dH). I've been using sodium bicarb. to keep this
> at about 30-40 ppm. pH has been about 6.9. Is there really a risk of a
> drastic pH drop with a 20% daily water change?

Not as long as *the tap* stays stable. Hopefully it will not bottom out or
move around too much. Supply is not a set level. That's what I'd watch more
than anything. 
Your plants can handle the low KH's for awhile. If they seem like they are
having problems or the pH moves around much add a touch more Sodium bicarb.
Try 2 KH if so. That's not that much and I really think it's not going to
make or break any Discus breeding:)
You have a pH monitor? I recall that you do and you can watch things closely
and the KH test is very quick.

> It would like to keep the pH
> and CO2 low with this naturally low KH. Given daily water changes with tap
> with this KH, how low can I safely keep my KH? Is 1.3 too low? With
> supplementary CO2, does alkalinity (carbonate) serve any purpose other than
> pH stability?

I think YOU can get away with it. Others might have more difficulty:) Get
your spawn and raise it back up and back off the water changes/feedings.
When your ready to do more work and breed again do this pattern once again.
I cannot see someone keeping this up day after day/month after month/year
after year. Commercial breeders make life as easy and automatic as possible.
Your going to forget or go out of town at some point:) Or neglect things(you
have a planted tank to still deal with also!) or get lazy. Maybe not?

The difference between 1.3 KH and 3 is not that great and provide for a
margin of error. How much margin you want is up to you. Better slightly
"stunted" fish that spawn less in a nice planted tank CO2 injected tank with
healthy plants than a bare tank set up IMO. The other issue of stunting are
questionable. A bottomed out tank with dead fish is the worst case IMO.
Keeping your CO2 at 10ppm or 25ppm with injection will not matter if your Kh
goes to zero. Fish will be hurting in either case. How much risk do you
want?

I'd relax a bit about all this Discus info. Grow them up and enjoy them and
the plants. I've had them do extremely well in high light/high CO2 plant
tanks. Feed them well and cater to the plants. When your ready to do those
water changes and increased feeding - go for it. After you get your spawn go
back to the enjoyment phase. Amano has said the mantra "Healthy plants
equals healthy fish". It applies here.

Rumor has it Amano is speaking at this years AGA in TN! Make your plans to
attend.
Regards, 
Tom Barr 
> 
> Thanks,
> Jared