I have a 9 gallon low tech planted shrimp tank. I currently have 12 bloody mary (neocaridina) with a horned nerite snail. They appear to be doing well so far and a couple of females are berried and no deaths, so I must be doing something alright.

I'm on my 3rd water change (once per week) but I have been wanting to do a minimum of every other week but have been afraid of the rising TDS. I know TDS rising is expected, especially since I fertilize twice a week. Nitrates are really low right now, around 5ppm at most after fertilizing twice a week. I'm not sure how to handle the water change process.

My tank started around 212 TDS, I use RODI with salty shrimp GH/KH (inert substrate). TDS is around 220+ before I did my water changes, which is weekly so far. However when I add in salty shrimp mixed water to my tank, the TDS stays around that 220 ppm or higher. That is where I am confused, how do I reduce TDS through water changes if I am only raising it each time? Or do I let TDS rise to a set limit and then start lowering it then?

Currently during these water changes, I remove about 10% and I slow dripped in half gallon of mixed salty shrimp water and then half gallon of straight RODI after to cut the TDS back down and to not raise the GH and KH further. I am trying to keep it at 6/7 dGH and 4 dKH and I measure during water changes.

Everything I've read online says to just add in remineralized water into the tank but doesn't address the rising TDS content with each water change. I feel like I'm completely missing something here. Am I over complicating it and should only reduce TDS as needed? Should I not be afraid to let TDS raise and allow nitrates to build up for my plants?

Side note, is it safe to add in KNO3 to help raise the nitrates for my plants or will it be detrimental to my shrimps and incoming shirmplets?

Edited January 8, 20224 yr by alkemist

2 hours ago, alkemist said:

Everything I've read online says to just add in remineralized water into the tank but doesn't address the rising TDS content with each water change. I feel like I'm completely missing something here

The reason this is happening is partially due to evaporation. Water evaporates and leaves behind minerals, thereby raising the TDS. Your next water change adds a bit more minerals, and the TDS slowly creeps up. The cycle continues as more water evaporates. Over time, TDS is way above the stating point of 212. 

Of course there are other factors that influence TDS level creep.

There are a few things to minimise it.

• Continue your weekly 10% water change.
• Use pure RO to top up tanks.
• Once a year 100% water change. This resets the minerals in the tank.

 

2 hours ago, alkemist said:

Side note, is it safe to add in KNO3 to help raise the nitrates for my plants or will it be detrimental to my shrimps and incoming shirmplets?

Not a good idea. High levels of Nitrate is detrimental to shrimps.

Try to keep low light plants in a shrimp tank. That way, you don't need high light and fertilisers.

I imagine the fertilizer adds TDS also. I wouldn't use plant fertilizers with shrimps it usually doesn't go well long term and probably 90% of the time isn't needed anyway. If you do eed fertilizer then use the minimum you can, if foor instance you  have an inert substrate such as sand or gravel!

Otherwise JayC has it covered, with evaporation and using pure RO water for topping up between maintenance.

It looks/sounds like you are doing well so try not to get too fixated on exact TDS numbers.

If you want to reduce the TDS from 220 to 200 then when you do your next 10% water change just use pure RO water dripped in to the tank. This isn't as extreme as it may sound, after all that is what would happen in the wild when it rains!

Edited January 19, 20224 yr by sdlTBfanUK

Thanks for the replies. For some reason I wasn't notified about the replies ?