Just a thought

[Austex]

I have a 8 gallon shrimp tank that is heavily planted and has a Fluval Nano filter. After several months of operation, the Nitrates and Nitrites are always zero. So I have been just topping off the tank with RO water and adding some plant and shrimp nutrients as needed. Is there any reason to do a water change when my water parameters are always fine?

I am not trying to avoid doing a bi-weekly water change.

[IvanSanchez]

I would stop the RO top offs.. Shrimp and or any other fish can not live off of pure RO water. How ironic right? Pure water should mean good, healthy water but it lacks need minerals.You need tap or add back the needed trace minerals that tap water contains. You run the risk of your shrimp and plants depleting the minimal amount of minerals in the water and WILL cause deaths.

Weekly water changes with a percentage of RO water mixed with tap is a great way to go for lowering PH.

You also run the risk of phosphate build ups which can lead to algae.

Plus you should be weekly or biweekly gravel vacuuming. With out gravel vacs you run the risk of NH3/4,NO3/2 pockets in substrate that if disturbed in the future can lead to bad results.

Plants or a nano filter can't deal with shrimp waste either!

Just my 2cents

[Mzungu]

What kind of shrimp?

And I'm confused about your last statement. Do you mean you're still going to do bi-weekly water changes, or that you want to stop doing them?

[Austex]

I have CRS in a Fluval 8g tank. Since the quality of the tank water is always very good, I was considering only doing monthly (or longer) water changes. I have read some post from users that have accidentally killed their shrimp after a water change.

Just considering options.

[Mzungu]

I think this is a really good question! Heavily planted tanks are almost always going to have no nitrates/nitrites. And by topping off with RO water, it's true that you're not adding any "minerals" and such, but you also said that you're adding "shrimp nutrients." What exactly are you adding?

I have a 5g planted CRS tank, and I have to say that in the past, without frequent water changes, I've had CRS that didn't really thrive. But with this tank I'm doing weekly 50-75% water changes, and they're producing babies like mad.

So, anyway, I don't know the answer. :) Are your shrimp still making babies? That's usually how I gauge whether or not certain inhabitants are happy with their environment. I guess it's not very scientific, but it makes sense to me.

I also have a planted RCS tank, 5g, and have noticed that the less water changes I do, the less babies appear.