Automatic Water Changes w/ LiterMeter III

[Heiko11]

Just read Mike Cao's article on Advanced Aquarist. In it he mentions using a LiterMeter III to do automatic water changes. I'm moving from a 120G to a 300G system, and this sounds like a great idea, but I've a got a couple of questions ..

1. I currently use an ATO to deal with evaporation. Do you still use an ATO with this set-up? If so, how do you prevent it from being triggered constantly by the auto water change? If not, how do you account for evaporation ... seems like the water change topping off the sump would increase salinity over time?

2. Do you have to deal with evaporation in the fresh salt water source as well to avoid changes in salinity?

3. Any other 'gotchas' I should be aware off with this set-up?

Any perspective/advice from somone using this water change set-up with the LiterMeter or similar dosing system appreciated!

 

[Anonymous]

For his 155 gal system with a 5 gal/day water change, it is very costly. At this aggressive rate, which can be justified due to the heavy feeding and non-synthesis nature of the setup, there is only a minor evaporation issue. If the new saltwater is at the right salinity level, the system should be only slight more saline than the new saltwater used for water change. It does not get much more saline due to the aggressive water change schedule.

For these setups, the ATO system is recommended to be monitor by salinity (conductivity) meter, not water level. Either the system salinity (preferred) or the new saltwater salinity should be monitored, but it is not necessary to do both. The fresh RO will only added to the system when salinity is increase above a threshold, not when the water level frustrate during water change cycle.

 

[Heiko11]

I wasn't planning on going quite as aggressive on the water change volume (although at 5gal/day that's just about a 10% weekly change on a 300G), but the idea of using a salinity meter to drive the ATO makes sense. Any suggestions for ones you found work well in that application (ie on 24x7 reliably)?

 

[Anonymous]

There are not many choices when it comes to conductivity controller. I have no particular recommendation for you at this point. You may want to check out some vendors and see what is available for the hobby, or adapt one of the industrial controller used in chemical process control application.

FWIW, 10% weekly water change is also aggressive. Depends on your bioload and setup, some system can go for months without water change. But with regular feeding and low-nitrate requirement, you will need to do maybe 5% weekly or 10% monthly water change. When a system is recently setup, you will need to monitor the water parameter more closely and adjust the water change schedule accordingly. As the system mature and stabilize, you can do away with periodic, but less frequent monitoring of water parameters. One of my tanks is at a point where I can do just several water changes a year, for example.