Why a reverse photo period for a refugium?

[OttawaReefer]

I've got a 10G refuge and read somewhere that people would recommend a reverse photo period from the actual tank.  I'm wondering why having a reverse photo period would be better than one at the same time as your main tank.

There must be something I am overlooking as to why it was recommended to be reversed, but I just can't see the logic.

[Vincenzo.]

i run my fuge 24/7....boombap!

[ramblnpony]

I believe it's to boost oxegen and stablize PH that normally go down during the Display Tank night time hours. 

[mikerobart]

Mainly stabilize ph.

[OttawaReefer]

Ah, if it's just to stabilize Ph.....I'm not sure if that 10G is going to do much for a 90G + 20G sump.  There just isn't, and I believe that there should not be, that much water flow through the refuge in the first place.  My fuge is water fed by a reduced split off from the downline of the overflow.  It doesn't provide a huge turnover in the fuge....but there are tonnes of little white buggers on the glass, so it seems to be enough.

If it's just to help stabilize Ph I'll run the photo period the same as the rest of the tank.  I've got a 65w bulb in there and the light spill from it kind of defeats the "dark period"  for the main tank.

[reefdava16]

Youd be surprised at how much the fuge can help. Why not conduct a test for yourself to see if it is worth it. Test at night when all the lights are off then test again the next night when the fuge is on.

[mikerobart]

If you've got a ton of macro algae under a bulb that is good at growing it (basically any bulb ! ).. it's going to in all likelihood make a noticeable difference. Now on your particular system it may or may not matter, and maybe the benefit would not be noticed even if the difference was significant but can't hurt. I am sure either way is not going to make or break things.

Photosynthesis raises pH, and cellular respiration lowers pH. When you turn off the lights in the display, photosynthesis stops, so CO2 utilization stops and pH will drop. A reverse photoperiod will prevent the drop from being as significant because photosynthesis will be taking place elsewhere. Anything that promotes stability is probably a pretty good thing.

I think the diurnal swing our tanks experience is quite a bit more than what you'd see in nature... I don't have any good evidence other than a sense that we pack them pretty full of coral in a limited water volume and there would be less buffering capacity.

[OttawaReefer]

The photosynthesis period makes sense.  Not sure if that little ball of chaeto I have in the 10G sump is going to do much photosynthesis to keep the PH swing on the 90G display tank from going too far.

I'll start checking the PH between lights-on and lights-off, and then do the same with the photo period reversed.  It will at least be interesting to see how much correction it does.

[Hookup]

i run my fuge 24/7....boombap!

Do you have your lights on your fuge 24/7 Vince?

[mikerobart]

Yah will be interested to hear the results as well... my fuge is not very big either on my 90g. Actually about 1/3 of my 33g sump so say 10g ...

Although the different photoperiods also would have an effect on macro growth and hence nutrient export. I guess maybe there would be a trade off.

[salvini55]

I run my fuge 24/7 as well. The ph swing is a little less but not rock solid. before the fuge it would be between 7.5 and 8.2 now it is between 7.8 and 8.2 on the RKL.