75 Gallon Powerheads
 

I have a standard 75 gallon tank. On the back right i have 2 Hydor Koralia Nano Stream Powerheads 240 GPH Each. On the left side i have 1 Hydor Koralia Nano Stream Powerhead 565 GPH . That should give me 1045 gallons per hour not counting the return pump. My question is this. My corals especially my kenya tree is not happy and some of the other corals dont seem to be growing. My water is great as far as parameters go. I am running black box lights. Can the problem be i just dont have enough flow or maybe because these pumps are Nano Streams not a wide enough flow. Any suggestions would help. Possible changing out the 2 heads for a bigger one and leave the 565 on the opposite side? Thanks.

You could probably use a little more flow, in my opinion, but I would that isn't the problem.

What are your actual parameters? At least for s.g., temp, alk, Ca, nitrates, and phosphates?

Definitely need some more parameters to help diagnose. I have a 75 also and only have one MP40 I the right side pane, towards the front. My return comes out of the right back which I have pointed to the left also. Now, your rock formations will make a difference, (I have an island on each side) but I have no dead spots, Most SPS are on the left side island, and all the lower flow corals are happy down low.

I have a 75g with two RW-15s on each side...

Independent of possible light and water chemistry issues (which I cannot hazard a guess without details), I would surmise that you have relatively little flow - those pumps are called "Nano" for a reason, as they are meant for smaller aquariums (40 gallons and under). I use the Koralia 240 in my 9g jawfish tank for example, and a pair of the Koralia 565 in my IM Nuvo 20g.

Since you do not have an issue with cords in the display, there are a number of relatively inexpensive options available to you: IceCap Gyre 150 (controllable w/ max 3000gph at $150), pair of non-controllable Tunze NanoStreams (which unlike the Hydors, refers to the size of the pump, not the aquarium it is to be used in, but similar in concept) size 6025 (740gph at $45 each) or 6045 (manually adjustable 1175 gph at $75 each), or any number of cheap Jebao pumps (I personally don't recommend due to quality issues, but others swear by their longevity). One could also consider the controllable EcoTech Vortechs w/ their motor outside the aquarium, either a pair of MP10's or a single MP40 (much pricier than previous options).

If $$$ is an issue, and for a 75g display, I personally recommend the Tunze pumps or the IceCap Gyre, and if it is no issue, then I still like the Vortechs. Full disclosure: the only pumps I don't use currently (or have used previously) out of the options listed above is the IceCap Gyre, although I have thought about trying one out when there is a sale in the future... :)