High tds

[Jason A.]

I have a 40 breeder with a plenum 307 fluval canister fliter.

I've had a higher ph than I'm comfortable with roughly 7.4-7.8

The normal other tests are ok but I used a tds meter and found I had over a 600 reading so I checked my gh/kh and my kh changed at 3 drops,  but my kh didn't change even at 30 drops so I did a 10% water change and the tds read 470(ish) and now a day later reads a little over 500 I'm planning to do another water change in a few days just don't want to change much to fast so I can save what fish I have left.  I purchased 20 cardinals and after I added 5 apistogramma agassizii the cardinals started dropping off 1-2 every other day and now I have 1 apistogramma and 5 cardinals remaining 

[Minanora]

What substrate do you use? & What media is in your canister? I've recently started using a tds pen in my tanks. I don't have a lot of advice regarding the readings. But I know you can work on getting the readings down by doing water changes with RO water and it really helps get tds, pH, and KH/GH down. Been slowly getting things down on all of my tanks this way.

Once a tank gets where I want it, I then mix ro and tap water to get the same parameters for water changes, let it sit for a few hours before testing then put it in the tank. On my biggest tank it can be a pain but I hardly ever need to change water in there so it's not so bad.

Also, to address the low KH, crushed coral could be a good solution. You can put a small baggie in your canister.

Edited December 11, 2021 by Minanora
Phone auto-correct...

[Mmiller2001]

Cardinals and Apistos really enjoy soft water! I keep my water at 145 TDS, 5dGH and 0KH. Don't be afraid of lowering KH. 

I would do 10% water changes, with distilled water, every other day until my GH was down. I would ignore KH and pH. You could even go every 3 days if you are worried.

5dGH is plenty for those fish, and plants will appreciate it too. PH "crashes" is an old wives tale. GH, KH and TDS are way more important than pH.

As mentioned above, remove anything that could be actively raising TDS. Things like non inert rocks, shells or decorations.

Edited December 11, 2021 by Mmiller2001