[SardinePatheNews]

low tech 30 liter shrimp tank, 1 large amazon sword, some anubis, java fern and then water lettuce and duckweed floating

today i added ferropol for the 1st time (other ferts are available etc) , i had seen some yellowing on the anubis so thought i should add some iron and it turned up yesterday.
Before water change the tank sat at tds 305, i used my usual 3:1 ro/tap mix though didnt measure it today it should run at around 220 tds, i added 1/2 mil or ferropol to this too as directed for water changes . I did not do an initial dosage of the tank, this 1/2 ml is all it has seen.

this evening, maybe 8 hours after the change i checked the tds again expecting to see a 25ish drop in tds, same as last weeks but no

the tank tds 8 hours after adding 2lt of 220ish water to 28lt of 300ish water was 150 , adding ferropol is the only change to routine and seem to have resulted in half my tds vanishing

where did it all my tds go? (not that i'm complaining, just a bit baffled...)

update: re-checked this morning 18 hours after the change and tds down to 130

 

[Mark Fisher]

The most likely reason is the TDS in your tap water is less than you think it is. Has it been raining in your area lately? After a big rain, the TDS of surface water can drop quite a bit.

 

[SardinePatheNews]

the tap water makes up <2% of the tanks volume, its not going to change tds much even if i swoped it out for pure RO , i'm sure this is the work of the ferts somehow. gh/kh havent changed at all, could the ferts being an iron and trace element supplement be changing the water conductivity and so mess with the tds meters accuracy?

edit: scratch that theory, fresh glass of treated tap, added a generous splash of ferts and tds jumped up 100 or so

 

[Mark Fisher]

If you're using 3:1 ro/tap as you stated above, your tap water is 25% of the volume, not <2%.

 

[germanblueramlover]

For a 2l water change on a 30l tank, the amount of treated tap would be about 2% of the tank's water volume.

edit: scratch that theory, fresh glass of treated tap, added a generous splash of ferts and tds jumped up 100 or so

When you tested this today, was the initial TDS of the tap where you expected it?


If it really did plummet after adding the ferts, the only thing I can think of is that they precipitated out in the tank.

 

[SardinePatheNews]

The tap water was <300 , the tank was checked on Saturday at 300 and then water changed Sunday afternoon, rechecked Sunday eve

I've changed the battery with no difference , or no difference upwards, today's reading is 95

Mains water here is normally pulled from the limestone aquifer as 750-800 tds calcium soup, could be they've switched to reservoir water to cover the end of summer .

As no one here chimed in with a yes that always happens with ferts I'm thinking maybe the meter has gone into landfill mode , I ordered a new one yesterday (allegedly arriving today) for a second opinion


update:
Smell the glove is here!! freshly unboxed new meter shows 330 which is close to expectations so seems the old meter had gone belly up overnight