HCl (hydrochloric acid) will burn off the water's buffer. Carbonate and Bicarbonate will be converted to CO2 and degass. If you go this route, approach it with caution.
The following procedure will achieve this end. However, it's not to be approached lightly and will require a massive amount of work for a tank of this size.
I would suggest doing it by incremental dilution. It's the safest way, but more work intensive. Esp. at this volume.
You're going to need a fair bit of acid to bring it down.
Use a gravel vac to syphon out a bucket load of tank water. Drain the bucket and refil with tap water about 3/4 to the level removed from the tank.
Add enough acid to bring the pH down to about where you want it (6.8-7.2) or a little lower, do it small amounts at a time! Take heed though, you may see no change for a long time then the pH will crash, you've got a strong buffer. I suspect that you have a little wiggle room, the amount you'll be working on is such a small fraction of your tank.
After you've done this, top off with additional tap water to the original volume removed.
Once you've figured out how much acid you need to add to each bucket, the process will be quicker.
By doing this you'll be continually removing higher pH water and replacing it with lower/correct pH water. The tank params. should change very, very slowly.
I don't envy you the workload. Really, get on that new RO unit ASAP. You may also want to suppliment this by buying some bottled water to help speed the process.
Caveats:
How are Arowana's about Cl? You'll have a fair bit of Cl ions left in your tank by the end. In other words, you'll decrease pH and KH but increase salinity. If I can recall off the top of my head, the increase to salinity will probably be negligible, i.e. probably too small to pick up on any hobby equiptment, but be aware of this.
Approach with extreme caution and be very, very careful handling HCl. Wear gloves, work clothes and safety goggles. Muriatic acid is more dilute than your standard lab stock, but still amply strong to cause injury.
The following procedure will achieve this end. However, it's not to be approached lightly and will require a massive amount of work for a tank of this size.
I would suggest doing it by incremental dilution. It's the safest way, but more work intensive. Esp. at this volume.
You're going to need a fair bit of acid to bring it down.
Use a gravel vac to syphon out a bucket load of tank water. Drain the bucket and refil with tap water about 3/4 to the level removed from the tank.
Add enough acid to bring the pH down to about where you want it (6.8-7.2) or a little lower, do it small amounts at a time! Take heed though, you may see no change for a long time then the pH will crash, you've got a strong buffer. I suspect that you have a little wiggle room, the amount you'll be working on is such a small fraction of your tank.
After you've done this, top off with additional tap water to the original volume removed.
Once you've figured out how much acid you need to add to each bucket, the process will be quicker.
By doing this you'll be continually removing higher pH water and replacing it with lower/correct pH water. The tank params. should change very, very slowly.
I don't envy you the workload. Really, get on that new RO unit ASAP. You may also want to suppliment this by buying some bottled water to help speed the process.
Caveats:
How are Arowana's about Cl? You'll have a fair bit of Cl ions left in your tank by the end. In other words, you'll decrease pH and KH but increase salinity. If I can recall off the top of my head, the increase to salinity will probably be negligible, i.e. probably too small to pick up on any hobby equiptment, but be aware of this.
Approach with extreme caution and be very, very careful handling HCl. Wear gloves, work clothes and safety goggles. Muriatic acid is more dilute than your standard lab stock, but still amply strong to cause injury.
