First Saltwater Tank, Hard Water!

Discussion in 'Saltwater Beginners' started by RandomFirefly, Jul 13, 2019.

  1. RandomFirefly

    RandomFireflyNew MemberMember

    I've set up my first saltwater aquarium. It's a 40 gallon acrylic hexagon style which I intend to house a Peacock Shrimp in. The substrate is a blend of crushed coral and live sand. The plants are fake but there is an arrangement of live rocks and one piece of small driftwood in addition to some ornamental burrows for the shrimp.

    I purchased store bought reverse osmosis water and used Instant Ocean salt to mix into the tank. After 24 hours of the initial set up I tested the water and the pH, hardness, nitrates and ammonia were all good. So as a test I introduced two turbo snails and two emerald crabs. Another 24 hours and they are all alive and well and my water testing again showed good numbers.

    It is now 72 hours and my testing kit showed everything was good EXCEPT for some reason my water hardness is at the highest level. Why is this? I don't even really understand how reverse osmosis water can be hard. The filter is working fine, the thermostat is fine, the salinity levels are good and all the other readings are normal but the hardness went from normal to maximum reading. I tested again and same results. What is causing this and is it a danger to my critters?
  2. MrBryan723

    MrBryan723Well Known MemberMember

    Hardness is just the amount of dissolved minnerals in the water. Seawater is supposed to read very hard. What I'm not really understanding here is why your first 2 tests didn't read as very hard as well, because they should have.

    Is this a brand new tank? Has it been cycled or just set up?
    Last edited by a moderator: Jul 13, 2019
  3. Jesterrace

    JesterraceWell Known MemberMember

    Are you using RODI water?
  4. coralbandit

    coralbanditFishlore VIPMember

    Last edited: Jul 14, 2019
  5. CheshireKat

    CheshireKatWell Known MemberMember

    I've never had a saltwater tank, so I don't have personal experience and I honestly don't know much, but I recently took an Oceanography course. What stands out to me the most here is the crushed coral and salt. Dissolved crushed coral and crushed shells in the water is what causes the alkalinity and higher pH of the ocean (the ocean pH as a whole is around 7.8-8; the deeper seafloor is harder with a higher pH than the very surface due to the accumulated minerals and such from shells, dead coral, etc.). Crushed coral is often used in aquariums to buffer up pH (at least in freshwater, I don't know about saltwater, but I'd assume so).

    I'm guessing that the substrate and salt might've started to dissolve more and mix with your water, which is why your initial readings didn't show a hardness change for a few days.

    But as I said, I have no experience is saltwater tanks. I just thought I'd chime in in case it helped and/or people with more experience and knowledge could build off of my thoughts.
    And your pH remained the same, right? It didn't increase or anything?
  6. Momgoose56

    Momgoose56Well Known MemberMember

    Crushed coral can raise GH, KH AND pH. Did you cycle the tank? What test kits are you using to test your water?
  7. CheshireKat

    CheshireKatWell Known MemberMember

    Yeah, that's why I'm confused because there was no mention of the pH raising. I'd expect that with RO water and crushed coral substrate, a rise in each would be seen. But I've had no personal experience with RO or crushed coral, so :emoji_shrug: I'm just going off my meager knowledge.
  8. Momgoose56

    Momgoose56Well Known MemberMember