Changing GH and KH?

[daveyboy]

Hi everyone. I have a question about GH and KH. Does it naturally decrease over time?

I finally got my ebi cycled and parameters right last week so decided to finally add shrimp.

Sunday Dec 18
pH 7.2
Ammonia 0
Nitrite 0
Nitrate 10
GH 5
KH 3
Added 4 Amano shrimp and 3 Cherry shrimp

Tuesday Dec 20
No deaths and all seem to be active and feeding so added 4 more Cherry shrimp

Thursday Dec 22
One Cherry death

Friday Dec 23
One Cherry death - possibly molt related?
One Cherry missing - possibly dead and eaten?
pH 6.4
Ammonia 0
Nitrite 0
Nitrate 5
GH 0-1
KH 0-1
The rest of the shrimp are active and feeding.

All seem to be active until they molt then they stop moving then die. I think the most likely culprit of the deaths is the low GH/KH and I know I need to boost these but the question is, why did my pH/GH/KH change from 7.2/5/3 to 6.4/1/1 in a matter of days?

Since I added the shrimp I did no water changes or top off the water. The only water added was during the transfer of shrimp and this amounted to about 500ml added. I'm using the fluval substrate that came with the ebi. Tank is moderately planted. Using the Fluval mineral supplement and Seachem alkalinity buffer to adjust GH/KH.

Any insight would be greatly appreciated.

[BelieveInBlue]

If you just let the water sit there, the GH and KH will remain as it is. However, anything you have in the tank could lower/raise it; plants will use the minerals that make up GH for nutrients, and shrimp use the carbonates that give you KH for building their shells. Water changes will also change the KH/GH. There may also be chemicals in your water that are affecting the ions which give you hardness; something could be reacting with it or removing it. Your pH is directly affected by your KH: KH is essentially your tank's buffering capacity; the higher it is, the more difficult it is to altar the pH, so what likely happened is that, because your KH dropped, by a lot, something in the tank, which would normally do nothing significant, caused your pH to plumet.

Aside from the shrimp, What else is in your tank, both live and dead/artificial? Also, are you using anything like carbon or zeolite in the tank?

[daveyboy]

Thanks BelieveInBlue for the info. No deaths from last night but the missing cherry shrimp probably died and the evidence consumed. No carbon or zeolite in the tank but the filter contains added Biomax. The surviving shrimp appear to be active and feeding. So far I've only had deaths with the Cherry shrimp and none with the Amano shrimp. I've boosted the GH and KH the last couple of days and will check my parameters when I get off work today.

Essentially this is my tank:
Fluval Ebi 7.9 gal.
Fluval Stratum substrate
Fluval Mini Power Compact Lamp
Fluval Nano Filter with added Biomax
Fluval 25W heater

Plants:
Bacopa species (not sure if it's Bacopa Caroliniana or Bacopa monnieri)
Echinodorus amazonicus
Echinodorus tenellus
Marsilea quadrifolia
Vesicularia montagnei attached to drift wood
A few aquarium pebbles.

Livestock:
4 Amano shrimp
4 Cherry shrimp

Again no water changes and about 500ml added when introducing livestock. I think the issue is I didn't boost GH/KH when cycling the tank (it was essentially 0.) I only added Fluval mineral supplement and Seachem alkalinity buffer after the tank was cycled and before introducing the shrimp. Is it possible that the plants sucked up all the minerals since they were depleted during cycling (cycled for about a month)?

Dave

[BelieveInBlue]

It's not likely that they'd drain the minerals that quickly, unless you didn't add a lot of it, although it is possible. I believe the Fluval stratum is supposed to help keep GH stable, and since the swords are root feeders, the minerals in the stratum should keep the plants, the swords especially, from draining your GH. As for the KH, I'm not sure; I've had that happen to me before as well, but once I added a bit of alkaline buffer the KH stabilized.

[daveyboy]

Hmmm...mystery then. Atleast no deaths today. I've been boosting the GH/KH the last few days so hopefully future problems have been averted. Now pH 6.8 GH 4 KH 2. Will try to boost a little more. Looks like I'll have to do water testing more frequently now until stable.

[BelieveInBlue]

I would test first and see where everything's at before adding more chemicals; once it's in there, getting it out can be a real pain.