water mineral question

[zeebo]

I have read it is not good to just ''top off '' the tank with water because the minerals don't evaporate with the water... makes sense.. so what about removing 10% of the water and replacing with new ? Sounds like a stupid question, but are the minerals in the water colum or have they settled to the bottom ? Hate asking at the risk I sound dumb, but I need to know . This is tap water I am asking about.

Any info appreciated ,thanks.
Georgine

 

[macvsog23]

Hi

Your correct in assuming that just topping up evaporated water from a tank will increasing the TDS (totally dissolved Solids)
Stratification would cause the minerals to be suspended at different levels. As most tanks have a filter and thus water movement the minerals should be suspended over the water column.
A regular TDS or Kh test would show a build up if one existed.

 

[zeebo]

thanks Mac-
exactly what I needed to know, explained well. And thanks for quick reply.
georgie

 

[dw1305]

Hi all,
Same as Mac says, but it isn't a silly question at all. If you take calcium carbonate as your example compound (most of the compounds we are interested in are "salts"), it will be both in solution as bicarbonate/carbonate (measurable as the dKH) as the carbonate hardness, and also possibly will have come of solution as a ring of "limescale" or as lime deposits on the plants leaves etc. The reason it is both in solution and precipitated out as lime scale is because the water can hold different amounts of dissolved carbonates dependent upon it's temperature, CO2 content and what other salts are present.

All the dissolved salts (the TDS or conductivity we measure) are the same, they can go in and out of solution dependent upon temperature and pressure. It is only by adding water with a low salt load (RO, rain-water etc) that we can control the rise of the TDS as water evaporates.

Water changes with clean low TDS water also help to reduce nitrates etc. It is technically possible to have a planted aquarium where you just top up evaporation with RO water, but it is much easier to manage aquariums with regular water changes.

This is planted tank guru Tom Barr on no CO2, no water changes, low tech planted tanks <http://www.barrreport.com/showthread.php/2817-Non-CO2-methods>

cheers Darrel

 

[zeebo]

wow ,thanks for that info ! reason I asked is cuz I do a 10% wc-not vacuum ,daily, to keep my nitrates low (7), otherwise they can get out of control fast. It is easy to do with the python, takes a minute. On Fridays I do a complete vacuum. Just wanted to be sure I wasn't leaving too much TDS by doing the daily 10%.

I do have hard water and get alot of ''white deposit'' on the tank cover and around the rim,but rinse off easy enough. I can see water spitting up like seltzer or soda pop , when i remove the cover on Fridays. My tap ph is high ,but the wood brings it down to 6.8.

As for plants , they are doing ok, not great ,but alive. The tank is really set up to replacate a ''snag'' and plants not important, but got a few the phantoms don't touch now

many thanks , Georgie