Habitat - Outdoor :: Using RO water for pond

[alisonk]

Hi,

I have had our rescued RES turtle for about 4 months now, he is doing well, and growing. (now about 2 inches, and his shell has turned from greenish to brown). I have him in a preformed pond liner in our lanai (in Florida). I have 25 gallons of water in there. Unfortunately I cannot use our well water, as it has high sulphur. I have been getting 5 gallon jugs of the RO water that you can refill at our local supermarket for $1.50 each. Is this ok to use for the turtle tank? I have been testing it, but what worries me is that the PH tested very alkaline (the API test was dark blue, which was pretty much off the charts for alkalinity). I thought RO water was supposed to be neutral....?!
The GH and KH are low.
No knowing much about water, I was wondering if this was safe for the turtle, or should I be rather using something else? Maybe mix the RO with Spring water?

Thanks

[steve]

Are you testing the water prior to using it in the turtle tank?

[alisonk]

No, I tested the water that is in the tank already. Usually I just top it off when it evaporates, which is usually a 5 gallon jug per week.
I will test prior to adding, and see what the PH is of the RO water by itself.

[steve]

If you use RO water it may be necessary to add essential minerals back into the purified water. RO should be neutral, I'm, not sure why it would be very alkaline. Do you have bio media in your filter?

[alisonk]

Ok, this is interesting. I just tested the Pure RO water before I add it to the tank, and the PH was 6.4 - slightly acidic. I then tested the water in the tank, and it tested very blue, so PH must be 7.6 or higher - very alkaline.
I have a Fluval 106 external canister filter, and I have biomax in the bottom tray and a carbon sachet in the top tray. I have not yet changed the media since I set this all up, about 3 months ago. I just bought all new media, and was planning on replacing it (one type at a time) this week.

What do you think is causing the tank water to turn so alkaline? Should I do a complete water change? Does higher alkalinity mean that there are more minerals in the water? Perhaps the water is getting concentrated as it evaporates...

I just use some smooth river stones in the bottom (large ones), and have some floating pond plants, frogbit, water hyacinth, water lettuce and parrots feather.

When I change the media, which is best to change first? I also bought some nutrafin cycle for when I change the media.

Sorry for all the questions! I really want to get this right. We had a betta fish, and I also used RO water+minerals, it was a pain to get it right, and he ended up dying after a year and a half...I want our turtle to be comfortable!

[alisonk]

OH, one other thing that I just realized. When I clean the filter, I usually rinse everything in our well water, which has high sulphur. Will this negatively affect the bio media? Maybe I should use RO water to rinse the media too?

[ljapa]

Are any of the riverstones limestone?

Limestone is calcium carbonate. That will react with the acidic ph. It won't make it alkaline, but will raise it toward neutral. There may be something else in the pond that is contributing.

[alisonk]

I don't know what the stones are made of. I got them from home depot in a bag. I got one bag of white stones and one of black stones. I recall it said "river stone" on the bag. The white ones could indeed be limestone. Is that bad?

[ljapa]

Limestone isn't necessarily bad, nor is a high ph for a turtle. My tap water's ph goes up if you leave it for 24 hours. The tank varies between 7.8 and 8.2 ph.

True RO water is going to have little more than water molecules. That means it doesn't take much to change the ph. A ph below 7 means you have more H+ ions than you do OH- ions in the water. A ph above 7 means just the opposite. A particular ph reading is just a measure of the ratio of excess ions floating around.

In pure water with a 7 ph, you may still have H+ and OH- ions floating about, but they are in balance. Normally water from a tap, a well, floating in a pond has lots of other ions and stuff in it besides H2O. Typically some of that other stuff is going to pull out the H+ or the OH-. So, if you think of non-RO water, it probably has lots of other stuff and will tend toward a particular ph because of that other stuff that's either pulling out H+ or OH-. But, it will tend toward a particular ph value--at least until whatever other chemicals are used up.

RO water is really just H20 and H+ and OH-. Mix in something that is attracted to either the H+ or the OH- and the ph can change pretty quickly as a number of those ions are bound to the something else.

So, seeing quick and large PH changes for RO water added to water that has lots of other stuff isn't surprising.

From what I've read, turtles are more tolerant of ph and ph changes than fish are. That is based on what I've read, not what I've experienced though. However, my experience does show that a turtle is fine in ph around 8.

Steve is correct, though. You may want to investigate adding some of those essential minerals back to your RO. A turtle drinks the water it swims in, and it needs more than just the H20. Given that it's an outdoor pond, you probably have lots of those minerals entering the water, but you may still need to add more.

The thing about

[alisonk]

Do you think I should dump all the water and start over, with fresh media in filter etc?
Or would it be better to just start adding minerals into all future 5 gallon bottles of RO water from now on. I have some Kents R/O Right minerals left over from when we had the fish.
Also, Is it ok to keep rinsing the media in the well water or will this disrupt the friendly bacteria? We don't have any chlorine in the well water, the hose I use comes straight from the well. (we are in SW Florida, so its quite a shallow well). (Our house water goes through an aerator to remove the sulphur smell, then through a water softener, and a final sediment filter).

By the way, although this is an outdoor pond, it is under our covered lanai, so it doesn't get rained in, aside from the few splashes it might get being close to the screened side when it does rain (and it can rain quite hard here).

Thanks

[VeipaCray]

Straight RO is too soft to maintain a stable PH. The Carbonate Hardness aka Alkalinity measured in dKH but referred to as KH is very low in RO water. KH is essentially a way to measure PH buffering capacity. Generally speaking the higher the KH, the more stable the PH. Combine the low KH with low C02 and your PH will rise like you are seeing.

and have some floating pond plants, frogbit, water hyacinth, water lettuce and parrots feather.

Plants consume CO2. Lower CO2 = Higher PH.

http://www.advancedaquarist.com/2002/5/chemistry
http://www.tropicalfishkeeping.com/fres ... ium-73276/