Flow Rates and Small, Young Fish

[reefbyremote]

I have been reading here for months and obtained great advice/tips from many of you, thank you. Since mid September I have been setting up a 90 g witha 30 g sump. I have cycled the tank with cured live rock, sand and chateo obtained from a local hobbyist (thanks Darcy!) and some mollies who did very well. I now have no measurable levels of ammonia, nitrite or nitrates. The tank is full of invert life with lots of copepods, worms, small brittle stars etc. Corraline is growing as is some other "good" green algae. Their was also some gps, kenya tree, mushrooms and ricordea on the LR and it is doing well.

Here is the rub... I added 5 small (1 to 1.5 inch) green chromis from the LFS. All was well for the first week- they were active in the water flow and pick at any particles coming by. Then almost every other day we pulled one out of the overflow or sump. Then slowly over about 7 days one by one they exhibited a vertical mark on their sides and then after a couple of days died. We believe the mark is from the overflow.

I waited 3 weeks and then bought a dragon sleeper goby (sand sifting), 2 peppermint shrimp (for aiptasia- I have a little), and 2 x 1 inch true percula clowns. The first night (last night) one of the clowns went in the overflow. I pulled him out and he is now recovering-looking exhausted. I have turned off my powerhead for now. The other additions are doing well.

I am running my return pump and a single Koralia 3 powerhead. From what I have read this gives me relatively little water flow- in fact I was considering getting another powerhead to help circulation and move detritus. Now my fear is that I have too much water flow as it is for these small/young fish.

I would appreciate hearing about others experience on this issue. Thank you.

[Marlin65]

I had the same problem add bigger fish or turn down your return flow.

[hillegom]

Home depot sells gutter guard, to keep leaves out of the eavesthrough. Place that over your overflow, ie to cover where the water is flowing into the overflow.

[reefbyremote]

Thank you for the feedback Marlin 65 and Hillegom. The gutter guard or equivalent is a good idea. I thought the fish were all "playing" in the flow presumably looking for zooplankton. I did not realize they would tire as they did. I thought they would find a place to hide out of the flow when tired. I have turned off the powerhead to reduce flow and this seems to have helped. I will see how they do overnight.

[fkshiu]

Healthy salt water fish of the size that are sold in LFS should not have any trouble keeping up with a single K3 in a 90 gallon. That type of flow is miniscule compared to what these fish would encounter in the ocean. I strongly suspect that this was an acclimation issue or that the fish were already in a weakened condition when purchased.

[Marlin65]

Thats possible as well. Never thought about that.
How big is your return pump and your slots on the overflow?
Your in tank flow should not mater so hook that K3 back up.
I had a small file fish and one of my clowns get wedged up against the overflow and get killed, but I run a 3500gph Dart on my tank as my return.