Corals close up after topping off tank

Kal · May 12, 2018

After I top off my tank with RO water (0 TDS reading) all of my corals close up. Green star polyps, zoanthids, and a stony branch coral. They stay closed for maybe 1.5 days before they start to come back out. When I add the top off water I float a Lee's 2-Way Breeder on the top and pour into that so that it breaks the water flow and doesn't just surge onto the corals/rocks/sand. All of my water parameters are within range, and the corals look great once they come back out. Some Googling suggests this is the coral showing signs of stress, but everyone who has this problem describes it happening after water changes (which does also happen to me).

What am I doing wrong? I am adding a gallon of RO water to a 20 gallon tank when I do this maybe twice a week. I also add Instant Ocean Marine Conditioner every time just in case. Would getting an ATO solve this? Watching the BRS videos it looks like an ATO adds the water slowly as opposed to a full gallon at once. Is that what I am doing wrong? I need to top my tank off again but I am afraid of doing so without a better understanding of what is going on. Thanks!

Crabs McJones · May 12, 2018

Kal said:
After I top off my tank with RO water (0 TDS reading) all of my corals close up. Green star polyps, zoanthids, and a stony branch coral. They stay closed for maybe 1.5 days before they start to come back out. When I add the top off water I float a Lee's 2-Way Breeder on the top and pour into that so that it breaks the water flow and doesn't just surge onto the corals/rocks/sand. All of my water parameters are within range, and the corals look great once they come back out. Some Googling suggests this is the coral showing signs of stress, but everyone who has this problem describes it happening after water changes (which does also happen to me).

What am I doing wrong? I am adding a gallon of RO water to a 20 gallon tank when I do this maybe twice a week. I also add Instant Ocean Marine Conditioner every time just in case. Would getting an ATO solve this? Watching the BRS videos it looks like an ATO adds the water slowly as opposed to a full gallon at once. Is that what I am doing wrong? I need to top my tank off again but I am afraid of doing so without a better understanding of what is going on. Thanks!

Couple of issues. You're adding a gallon of ro water to your tank at a time. That means that your tank is going from a high salinity from evaporation to a lower salinity from dilution extremely quick. Also if your top off water is cold or room temp you're also dropping the temperature of your tank rapidly. Both are bad for corals. I would highly recommend either an automatic top off system, or if that isnt an option switch to manually topping off the tank daily. Do you have a set water level or are you eyeballing it? What I would also do is get my salinity set at 1.026 and mark the waterline, then you know exactly how much you need to top off at a time.

lzrlvr · May 12, 2018

Hi adding such a large amount of make up water to the system so quickly may be the problem.

Kal · May 12, 2018

Thanks all! I'm moving to a bigger tank in June so I'll add an ATO then as I'll have more room for a reservoir (moving into a house). For now, I'll add small amounts daily using a mark as you suggested. Seriously appreciate it!

Skep18 · May 12, 2018

+1 to swing in salinity. Continuously hearing how sensitive corals are to water consistent water parameters, my guess is they're kinda getting shocked by their surroundings.

Maggie321 · May 12, 2018

Just get the ato now, pretty small and nbd to move when it's time. I don't know how anyone could reef without one. I got the small tunze one and it's been the best thing I've ever purchased for the tank. It will make your life so much easier. I have 2 one gallon jugs under my stand and I go through about a gallon in 3 days. Easy to switch out, refill and mix my kalk to be ready in another couple days.

mike werner · May 12, 2018

ATO ATO ATO ATO ATO.unless you like the exercise.i'm out of shape because of my ato.

Kal · May 14, 2018

Maggie321 said:
Just get the ato now, pretty small and nbd to move when it's time. I don't know how anyone could reef without one. I got the small tunze one and it's been the best thing I've ever purchased for the tank. It will make your life so much easier. I have 2 one gallon jugs under my stand and I go through about a gallon in 3 days. Easy to switch out, refill and mix my kalk to be ready in another couple days.

I ordered the ATO linked below so that is on the way. I went with this one for the smaller tank because it is rimmed and this one wont require me to drop the water level super low below the rim. Now my questions becomes what about heating the reservoir water? I am using a 5 gallon jerrican to store the RO water. Do you have any experience with putting a heater in these? If I don't put a heater in here wouldn't I run into the same issue I have now? Sorry for all the questions, definitely want to get this right. Thanks!

https://smile.amazon.com/gp/product/B0195D3LC6/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
https://www.uline.com/BL_8191/Jerricans?keywords=water+container

Maggie321 · May 14, 2018

You don't need to heat it. It only adds a couple ounces at a time and that won't change the temp much at all.

Crabs McJones · May 14, 2018

Kal said:
I ordered the ATO linked below so that is on the way. I went with this one for the smaller tank because it is rimmed and this one wont require me to drop the water level super low below the rim. Now my questions becomes what about heating the reservoir water? I am using a 5 gallon jerrican to store the RO water. Do you have any experience with putting a heater in these? If I don't put a heater in here wouldn't I run into the same issue I have now? Sorry for all the questions, definitely want to get this right. Thanks!

https://smile.amazon.com/gp/product/B0195D3LC6/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
https://www.uline.com/BL_8191/Jerricans?keywords=water+container

I have the big brother to that top off. Works well. Only thing you need to watch out for (and I don't know if its the same for your version) is the magnet on the inside that sits in the water. They're known to rust out. All you do is contact coralvue and they'll send you a replacement no questions asked

What I did to help prevent that is take some aquarium grade silicone and put it around the seam so the saltwater cannot get in

chipmunkofdoom2 · May 14, 2018

Kal said:
If I don't put a heater in here wouldn't I run into the same issue I have now?

No. The problem is the magnitude of the change in salinity. Natural reefs experience currents and changing temperatures all the time. Temperature variance is not particularly problematic to saltwater aquariums. What marine ornamental fish and corals don't experience very often (if at all) are large changes in salinity.

You mentioned that you have a 20 gallon tank and you used to add a gallon of topoff water at a time. If you take 20 gallons of saltwater and allow 1 gallon to evaporate, you're left with 19 gallons of saltwater at S = 37 ppt (1.028 SG). If you add one gallon of fresh water, the water drops back to S = 35 ppt (1.0264 SG). That's a very large change in salinity, much larger than many reefers recognize as safe. This is why your tank is not reacting well to the topoff, not because the water is a different temperature.

If your freshwater reservoir is outside and is kept near freezing temperatures, then you may want to consider heating it. At that temperature though, you're going to have other concerns besides just heating the water. If you're keeping the reservoir indoors there are almost no concerns with regards to temperature and topoff water.