Adding Water To Compensate For Evaporation - Treat Or Not?

  • #1
I have a 10 gallon tank and am wondering if I should treat water added to compensate for evaporation (in between water changes) - I have Seachem Prime, which says a 5ml/capful dose is good for 50 gallons - what if I'm just adding a quart or two, a tiny fraction of that? Add a drop?

My concern, I guess, is chlorine from the tap water killing beneficial bacteria - does it matter if it's going to be so diluted?
  • #2
let it ride you don't need to dose for that small amount. Evaporation is not going to reduce your water volume appreciably unless it is super dry in the house or alternatively really hot and humid.
  • #3
Realistically if your only adding a quart or 2 of new water the rest should be enough to dilute the chlorine/chlorimine but I probably would add a drop or two justice to be on the safe side.
  • #4
Prime is 2 drops per gallon...I'd treat any water that you put in -- otherwise you're dumping chlorine in your tank.
  • #5
I would add a drop to the new water, any chlorine can be harmful to even less sensitive fish (much less any inverts you have).
  • #6
No amount of water goes in my tanks without being treated first. Why chance adding chlorine (if you have chlorine in your source water) to your tank when it is so easy to neutralize it first.
  • #7
I treat it! I don’t trust my water!
  • #8
I put a drop in usually if I need to top off, which is not often. Probably the amount of water I am adding it wouldn't matter much but to be safe I do it. Especially since my guppies come and swim into the water as I am pouring it (probably think they are getting fed)
  • #9
Let no chlorine enter my tanks ...without Prime!
  • #10
Question then if no chlorine enters the tank?
What about doing a water change with a python? Because the waters coming straight out the tap.
  • #11
Prime is dosed for the tank volume first in the case of using Pythons.

It's safe to add enough Prime to treat the whole tank every 24-48 hours, so it won't matter if you're adding a bit more than necessary to top-off water, as long as you're not overdosing the whole tank or topping off multiple times a day.

I agree with most here. Why take chances? Zero untreated water enters my tanks.
  • #12
Question then if no chlorine enters the tank?
What about doing a water change with a python? Because the waters coming straight out the tap.

I treat the tank before I fill with the Python, have not any any problems with it.
  • #13
I change 100ltr in one of my tanks every week I don't just treat the 100ltr I treat with prime for the total volume of the tank. With my shrimp tanks even top offs are treated and I use RO WATER and it's suppose to come out pure, but I wount take the chance
  • #14
Question then if no chlorine enters the tank?
What about doing a water change with a python? Because the waters coming straight out the tap.
Ok, we’re getting technical here so I edited my post. However, I add my Prime before allowing the water in.
  • #15
I agree with no chlorine.
I've been using API water treatment for the amount I'm replacing. Pouring it in the tank mixed with 5gal bucket as the python is filling Better to treat for the whole tank?
  • #16
Always treat your water. I have to top off my tank every day to every other day because it’s extremely hot and humid in my room with all of our reptile enclosures. I fill up a 1 gallon jug, add Prime, and keep it in my room for whenever my tank needs topping off.
  • #17
Answering the Walkman, IMO, it really doesn’t matter. I add a little bit of the Prime, pour some water in, add a little more, etc.
  • #18
I've got the room to do it so I keep a treated bucket of water around the house. That way it's at room temp and readily available. This may not be doable for everyone. I just use one of the 5ml tubes from the test kit and eyeball what I need.
  • #19
My roughly 30-gallon aquaponic system loses about two quarts per day to evaporation and respiration. My biggest stock pot is 3 gallons so I dechlorinate about 2 ¾ gallons at a time, adding replacement water as needed from 2-quart storage bottles. Chlorine will degas on its own in a day or two. Chloramine can be removed with a 20-minute boil (documentation; see bottom of page 28). I don't use Prime because it is not recommended for use with fish or plants intended for human consumption.
  • #20
I used to mix tap and RO for water changes, because my tap water had high phosphates (planted tank). Tap phosphates are now tolerable, but I still get a 5gal jug of RO water from the local depot every month or so just to use for top-offs.
A. It doesn't need to be treated.
B. At least on paper, I'm only replacing what has evaporated, not bumping dissolved solids or micros from tap water.

Beyond that, I'm in agreement with the majority that yes, you should treat anything that goes into your tank. At small volumes I doubt the fish would suffer before it's finished gassing off, but it's the bb I worry about.
  • #21
You don't need to treat for that small amount but you can also bypass the treatment by letting the water stand out for a few hours (usually recommendation is 12-24 hours) before adding it. If you know you top off regularly, then always just have some water ready to add that way.

Note that doing this should let the chlorine evaporate, but not necessarily other things like chloramines (as far as I know).

However, there is another factor that if you are doing water changes around every 1-2 weeks, there shouldn't be so much evaporation going on (unless you do...then take the other options to refill it), and then you can just fill up the water as part of the normal maintenance.

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