Having a hard time keeping fish alive

[Shane.P]

Hi there fellow reef keepers. A little about myself and my tank.
I've had fresh water aquariums for a very long time. I've always been successful at keeping and maintaining my fresh water aquariums and fish. Been in the hobby now for over 15 years.
My last tank was a 55gal, black sand with sunken driftwood. Picked up a 2 inch black ghost knife fish and and electric blue Dempsey. With a few other species. I had that tank for 6 years, knife fish was over 12 inches. LFS was shocked and said they never seen them get that large in captivity.
I decided I wanted to try my hand in the saltwater. I currently have a 65gal, tank size is 48" long 24" tall and 12" wide. A bit narrow.
I'm having a hard time keeping my fish alive.As for equipment.
I have a Tidal 75 HOB with the sponge, floss, carbon and then the rock media in that order. I have 2 mini power heads aimed at the surface for agitation. I also have two wave makers. A heater, and two AI 16 primes.
The tank has been running for over 9 months and it's been cycled.
Temp 77 to 78 Fahrenheit
PH. 8.0-8.1
NH3 0.25 or under
No2 0
NO3 10-15 ppm on average
API Saltwater Master test kit
dKH 9.0
Cal 440
MG 1365
Salinity 1.024
All four are Hanna tester
I'm getting my fish from a very clean and reputable lfs. They qt before fish hit the shelves and do dips.
Currently in the tank with no issues are
3 Turbo snails. 1 Halloween hermit, 1 blue leg hermit, 1 nassarius, 3 trochus, and a tiger conch. A Green star polyp, some zoas, a pally and small xena.
The fish I had, 2 clowns, flame angle and Royal gramma.
I feed my fish twice daily with a mix of foods from, flakes to mysis and algae pellets.
My issues begun when I started dosing 2 part and phytoplankton. I notice my fish where hanging out at the top more and honestly, struggling for air. The two clownfish I did not qt and they where in there for about 2 months.
The angle and the gramma where bought and qted at the same time for 40 days with no issues. All the fish died within 2 days and it was at night. Since then I've corrected my dosing mistakes and let the tank sit for 3 weeks with my weekly water changes and maintenance.
I've tried twice now with good water parameters and as soon as my lights start to ramp down the fish swim erratically. Settle down, then are dead in the morning. No apparent sickness or injuries that I can see.
I've even dipped them after the died just to check for flukes or anything else with no luck.

After the phytoplankton, my pods have exploded in population.
where am I messing up here, any advice or criticism would be appreciated. Pic of tank below. Thank you.

 

[KrisReef]

I’m guessing you have Oxygen issues with light making photosynthesis and keeping the fish breathing until lights out.

You could also have more Ricks in your tank where fishes could hide. A hob skimmer would increase O2.

Having the rubble in the filter instead of lots of rocks in the tank may be part of the problem with the O2 being reduced in the filter?

Edit I think you should check out this thread https://www.reef2reef.com/threads/how-i-would-start-a-new-tank.1002648/

 

[bushdoc]

^^^Same thoughts.
If you dosed “dead” phyto, it might’ve caused heterotrophic bacteria bloom causing oxygen depletion. If you dosed live phyto, at night photosynthesis stops and phyto consumes oxygen. You need either skimmer or more surface agitation, but less phyto.

 

[Mr. Mojo Rising]

Nothing really jumps out at me. I do agree with above, more rock is beneficial in so many ways, and a skimmer might help. 24" is deep to provide oxygen just from some surface agitation. And I'm not sure about those powerheads, they look like nano size, more flow is often good for a tank as well. Not saying any of this caused fish deaths, just something to look into for overall tank improvement.

 

[blecki]

Super easy to verify. Leave the light on. If the fish remain fine, it's oxygen depletion at night.

Add an airstone. It's a quick and easy fix.

 

[Shane.P]

Thank you for your replies! I'll try all the above after I put more rock and tank stabilizes again.

 

[00W]

Agree with all the above.
Tank is very sparse with little to no algae after 9 months.
More rock, skimmer,more biodiversity all great suggestions.
Keep us posted.

 

[Shane.P]

Thank you, will do. Is my huge population of copepods and amphipods any concern?

 

[Cthulukelele]

Also an aside you really don't need to dose 2 part in a tank stocked like that. At best you're wasting money and at worst you're wildly unbalancing the tank

 

[00W]

Also an aside you really don't need to dose 2 part in a tank stocked like that. At best you're wasting money and at worst you're wildly unbalancing the tank

^^This.
Wait until you really need to do this and hold off for a bit.

 

[00W]

Thank you, will do. Is my huge population of copepods and amphipods any concern?

Don't think that will hurt anything-the least of your concerns.