Flow - Corals are mad...

[Myka]

I have a 33g with about 60% lps, 25% sps, and 15% polyps. I'm constantly battling flow. My corals have HUGE polyp extention when I have lower flow, and have much less polyp extension to the point that some of them look ill when I turn up the flow.

I have my tank arranged with a "wall" of rocks, and the rocks don't touch the glass on any of the sides. I have an MJ1200 blasting across the back of the tank down low to keep the sand back there clean. This flow doesn't bother the corals because the corals are all out front. I then have two MJ400s on each up back corner in the traditional position of pointing to the center front. This doesn't give me much flow... 12x turnover, and I get detritus buildup and some dark grey "algae" in the low flow areas. But the corals are all very plump and all have excellent polyp extension including the sps. If I replace one of the MJ400s with an MJ1200 I get 21x turnover, but I get "polyp shrivel". lol My Torch, my Duncan, and my sps all have noticably less polyp extension.

Should I just stick with the 12x turnover? Or will they get used to the 21x turnover? If so, how long? I've had them at 21x turnover for 2 weeks before and they still look like crap. How do you guys get 60x turnover and keep the corals happy? I think mine would shrivel to nothing!!

Please help!
Cheers!

[ozyreefa]

How many times per hour does your main filter pump put out? if in the vicinity of 12 - 15x per hour i think the additional 12x from your existing powerheads should be fine, about the grey algae, you can either try and tinker with your live rock a little to try and eliminate dead spots of flow or just keep on top of detritus build up in the area, i strongly reccomend the former. I also have duncans and a torch and there is a fine balance between to much and not enough flow(should be just enough to tickle the duncans tentacles and a slow waving motion in the torch).Good luck

[m2434]

IME some corals don't mind a lot of flow, however, there are many that do. It is not an uncommon problem. Sometimes you can get away with a bit more but you sometimes need to be cleaver. I had about the same amount of flow, but wanted to redundancy, so I put some powerheads in/behind my rockwork pointed at the back rocks/glass. It took a while to get it right, so that the more sensitive corals, such as my frogspawn, didn't mind it. Either way, 10x flow is the recomendation in most books I've seen - i don't think there is any thing wrong with it. In my tank, I did it more for redundancy, I didn't want to rely on one pump. If it fails I don't want the water going stagnant.

[LobsterOfJustice]

The key to high turnover rates is lower velocity... more water coming through a more dispersed outlet. If you are wanting more flow I would look into Tunze (nano) streams, Hydor Koralia, Seio, MJ mods, etc.

[Myka]

Originally posted by ozyreefa
How many times per hour does your main filter pump put out? if in the vicinity of 12 - 15x per hour i think the additional 12x from your existing powerheads should be fine, about the grey algae, you can either try and tinker with your live rock a little to try and eliminate dead spots of flow or just keep on top of detritus build up in the area, i strongly reccomend the former. I also have duncans and a torch and there is a fine balance between to much and not enough flow(should be just enough to tickle the duncans tentacles and a slow waving motion in the torch).Good luck

Ya, they are both happiest when I put them in the deadest spot I can find. Neither of them seem to care for strong lighting either. In fact, my Duncan is the pickiest coral in my tank. Likes to be in the shade with no flow. Is that normal?

The detritus is building up where the rocks meet the sand, and at the bases of the corals in the sand.

I have an AquaClear turned down low (it runs my carbon and RowaPhos), and I have a Remora skimmer that is powered by an MJ1200.

[quote=M2434]I had about the same amount of flow, but wanted to redundancy, so I put some powerheads in/behind my rockwork pointed at the back rocks/glass. It took a while to get it right, so that the more sensitive corals, such as my frogspawn, didn't mind it. Either way, 10x flow is the recomendation in most books I've seen - i don't think there is any thing wrong with it. In my tank, I did it more for redundancy, I didn't want to rely on one pump. If it fails I don't want the water going stagnant.

My corals really don't seem to like the MJ1200. It's too much of a blast I think. I'm gonna take it out, and put another MJ400 back in. I think it might be best if I had two MJ600s instead... oi!

[quote=LobsterOfJustice]The key to high turnover rates is lower velocity... more water coming through a more dispersed outlet. If you are wanting more flow I would look into Tunze (nano) streams, Hydor Koralia, Seio, MJ mods, etc.

I think the only one of those that would fit in my tank would be a Koralia. Hmmm...maybe I should try one out.