fresh water top-off

[kolosy]

when topping off w/ fresh water, how much as a % of total system volume can you add without creating pockets of wide salinity gradients? or rather without creating ones substantial enough to hurt inverts?

 

[Gtstricky]

If you are really topping off you will not create any issues. The salt does not evaporate like water does. As long as you are constantly trying to maintain the same water level the salinity will not be an issue. I hope that makes sense...

 

[Sk8r]

What you need, with a 46 g, is an autotopoff system. It's under a hundred (ouch, yes, I know: but you can't be tied to that tank every 6 hours adding a cup of water---and a near-50 can evaporate a gallon every 24 hrs.) I used autotopoff.com and got a dual float system that didn't cost a mint, and was dead easy to set up. You put your fresh water in a bucket with a pump and connect it to this unit, with the float in your water, adjusted to level. It will feed water to your tank by the teaspoon, no gradients, no mistakes, if you just remember to switch it OFF when doing your water changes and make sure the topoff line stays put IN your system, not onto the carpet.

 

[kolosy]

well... i guess the question is still one of how much can you add at one time. if i let my water level drop halfway in a 46g (exaggeration, of course) and then dump 23g of fresh in there, yeah, it'll come back to 1.026, but for a while it'll be bad times.

i guess a more accurate question is how much can you add at one time without short-term adverse effects on the inhabitants.

 

[kolosy]

<a href=showthread.php?s=&postid=13039739#post13039739 target=_blank>Originally posted</a> by Sk8r
What you need, with a 46 g, is an autotopoff system. It's under a hundred (ouch, yes, I know: but you can't be tied to that tank every 6 hours adding a cup of water---and a near-50 can evaporate a gallon every 24 hrs.) I used autotopoff.com and got a dual float system that didn't cost a mint, and was dead easy to set up. You put your fresh water in a bucket with a pump and connect it to this unit, with the float in your water, adjusted to level. It will feed water to your tank by the teaspoon, no gradients, no mistakes, if you just remember to switch it OFF when doing your water changes and make sure the topoff line stays put IN your system, not onto the carpet.

yeah, that's coming. i need to get a new cabinet, move the tank onto the cabinet, move the fuge and skimmer underneath, setup overflows in the dt, and then add the ato w/ kalk in it.

whew.

i think i have some work to do!

 

[reefergeorge]

I wouldn't worry about it. It take a lot of fw to change the salinity of 50 gallons of sw. Anyone that has done hypo will tel you.

 

[Sk8r]

On the other hand---as in ice-skating, nothing good happens fast in this venue. Slow change to get into a disaster, slow change to get back. Only if you are right there when it happens and are correcting within minutes should you contemplate a fast change: if you get back from a trip, for instance, and discover your tank salinity is way up, solve it by topping off a little more than usual and dipping some water out to discard. If the reverse, due to a topoff accident, topoff with saline water until the correction is made.

Why? Invertebrates in particular can have their tissues exploded by adverse saline balance: it's called osmotic shock, and it may take days to die of it, but they are the most vulnerable. Fish also suffer. There's an analogy going around saying, well, yes, but in tropical rainstorms there's a wild change in salinity near the surface.
Well, yes, but the fish in the ocean aren't pent up in a glass box 2x2. They move when they're uncomfortable, and would seek better water for their comfort. Even shrimp can travel really fast when they don't like their environment.