Photoperiod

Pugio · Post by **Pugio** » Tue May 01, 2007 6:40 pm

My P. pugio shrimp tank is all over the place lately. I've had a blue-green algae problem in it and when daylight savings came around I decided to cut back on the photoperiod from 12.5 hours to 9 hours. This resulted in all of the females loosing their ripened ovaries (saddle) after the next molt. These shrimp were all collected at ~38 degrees N latitude.

I thought that was interesting since I collected some of them last October when none of the females had saddles - and they took ~ 3-4weeks to regenerate their saddle at a >12 hr photoperiod.

This got me thinking. Since equatorial shrimp have days =12.00 hours long for aeons, how sensitive are they to changes in photoperiod versus higher latitude shrimp? Are we supposed to choose a minimum photoperiod for all shrimp or do we go by latitude at which the species live? I searched the site but couldn't find much...

This was helpful: http://upload.wikimedia.org/wikipedia/c ... ength.jpeg . At 38N latitude and to replicate their natural photoperiod cycle, these shrimp exist somewhere between 9 hours (winter) and 15 hours (summer) of daylight. I guess anytime over 12 hours works great to simulate spring/summer - but it seems the optimal cutoff would vary by species...or not? Maybe its not even important as long as any freshwater species gets >12 hours. I guess my question is what is the minimal timer setting I need?

badflash · Post by **badflash** » Tue May 01, 2007 6:46 pm

I keep most of my shrimp at 12 hours. I don't think 9 hours hurts, but the abrupt change from 12 to 9 probably triggered winter in their genes.

Drop it down to 6 for a few weeks, then back up to 9 and see if they think spring.

Pugio · Post by **Pugio** » Sat May 05, 2007 7:48 am

Well I decided to turn the photperiod back up to ~12 hours and they started regrowing their saddle. Pretty amazing. Now I got a serious blue-green algae problem...I dunno what to do now. I don't suppose RCS would eat it.

badflash · Post by **badflash** » Sat May 05, 2007 9:23 am

When I've gotten BGA it is because the phosphates are high. Try doing more frequent water changes & test your tap water. I would also add floating plants that block light. African Frogbit works well in ghost shrimp tanks, but not as well in cherry tanks. I don't know this is the frogbit, as I also keep dwarf crays in the tank, but in tanks that I keep frombit and hornwort, I never see much algae of any kind.

Pugio · Post by **Pugio** » Sat May 05, 2007 1:17 pm

I'll try more floating plants - I also looked back for threads on this and I *guess* RCS do eat BGA...maybe I'll throw one in a see if it cleans it up. I know this isn't an algae forum but if RCS eat the BGA in the grass shrimp tank my problems will be solved. The grass shrimp sure won't touch it. I also think it builds up on them between molts...

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Post by **Mustafa** » Sat May 05, 2007 1:33 pm

RCS only eat certain types of BGA (there are many, many species). They don't eat the nasty smelling, dark blue-green type at all. Just for further clarification.

apistomaster · Post by **apistomaster** » Sun May 06, 2007 5:52 pm

Maybe somebody has already discussed this but as a follow up to Mustafa's advice about water changes I would include hydrovacuuming the substrate as well. I always use a plug of filter floss inside the vacuum tube so the small zoae are not lost. It doesn't cost all the other copepods a loss of numbers either but silt sized debris is removed and anything that contributes to cleanliness but not to excess seems to help. Managing the photoperiod is as important as anything . It is hard to say why sometimes the undesireable algae get so well established in one set up and not another but either way I don't depend on the shrimp for algae control. Algae is always present enough to satisfy the basic needs of the RCS which are what I have the most of.