Question about the benefits of evaporation

[TomD]

Where this is my first small tank I got thinking about this. I was having heat issues on my biocube so was leaving the back hatch open and getting a good amount of evap so was keeping my salinity around 1.023.

I then discovered if I blew a small pc fan into the slots where the lights are it cooled the lights and eliminated the heat issue. By doing that and shutting the back hatch I now have almost no evaporation.

With such a small tank (29) I am thinking (maybe incorrectly), that this isn't good. Is the addition of some fresh RO water daily good for the tank rather than adding very little here and there ? I change 5 gallons weekly. No hair algae but small cyano outbreaks which isn't too bad and the tank is only a couple months old.

My thought process is that not having much evaporation and not putting fresh RO in every day will keep more nutrients in the tank?

Would appreciate input.

 

[JohnK]

Nope, only pure water evaporates so no waste is leaving with the evaporation. Pure water in, pure water evaps out (at least in theory).

Then again, gas exchange may be a concern if there is very little air movement over/around the tank.

 

[delta]

The fan should take care of the air exchange but would be better if he has(?) and skimmer

and as John stated the RODI exchange is of no issue unless the RODI has significant TDS

 

[Bobbofin]

Evaporation is normal. I have a 40 breeder with no cover with lots of water flow which causes more evaporation. Also have a sump 19 gallon sump too. I lose about a gallon every 2-3 days, more in the winter with dry forced hot air heat, less in the summer when I have the A/C set at 76° and unplug the heater. I have an Avast auto top off so my salinity stays spot on at 1.027.

 

[TomD]

John/Greg, there is plenty of gas exchange because I have my return facing upwards so it bubbles up a bit and the skimmer made for the bio cube works great and certainly creates enough.

Bobbo - I know at this point it is normal lol. My question was whether it matters but B said it best when I asked him today that less is better because the more RO you put in you are also depleting your calcium and other elements you need.

 

[JohnK]

And to add to that, unless your RODI is truely 0 TDS all the time (I know I rarely keep up with perfect RODI maintenance) you are likely still importing some contaminants with every drop of top off.

I only questioned gas exchange because I can't picture your set up so I didn't know if there was any ongoing air circulation over the tank. If that air were basically a sealed bubble over the (well circulated) water, the bubble of air wouldn't be able to mix with the larger atmosphere, and thus could become stale. Otherwise, yes, all about the water circulation

 

[TomD]

Because of that I don't shut the back hatch completely I just rest it so there's room for air to be pulled in.

 

[delta]

It doesn't matter. If you are replacing evaporating water the elements and calcium do not evaporate they stay in the lower volume of water after evaporation then are absorbed by the same factor when the tank is topped of. So it is a zero sum.

 

[TomD]

greg-ty