What should I do?

I have had my 38g tank setup now for around 9months. I currently have 2 clownfish 1 lemon peel 1 feather duster, 7 certh snails, 3 astrea snails 1 button polyp, 1 other coral.
2 months clownfish was added
3 months (3) peppermint shrimp was added ( lasted a month at most )
4 months crab, cleaner, button polyp was added
6 months lemon peel was added
6 months watchman goby was added (lasted a month at most)
6 months coral was added

I have added the snails to the tanks in small quantities over time. At one point I had around 15 astra snails.
My problem is I have had a hard time keeping things alive except for the fish, I recently had many astra snails die, and then the crab and the cleaner shrimp. I talked to my lfs and he said most likely one snail died, I didn’t see it and spiked the ammonia which eventually caused the nitrate to spike etc… Next thing you know your snails are dying off and causing major changes in the water which affected the crab and shrimp. At that time my nitrates were around 35. I have since stabilized the tank with water changes. Currently all my fish and certh snails (not astra) seem very healthy. I was down to 1 astra snail which didn’t move or stick to the glass, he was alive though. I added 2 more to see how they would react, and they did great for 1 week, then I noticed them barely clinging to the glass and then eventually falling to the bottom. They are alive however they just don’t move, I think it’s a matter of time.
One other thing when the nitrate spiked from all the carnage the coral closed up and I’m having issues bringing them back to normal.
I do weekly water changes of 4-5 gallons with (instant ocean salt). I don’t let the water sit over night, or bring it up to room temp. I do use a ROI 4 stage. When I Add the water I add it over a 1hour time, slowly trickling it into the tank. I have seen the tank drop from the normal 78 to 76 when doing this, I’m not aware of this being a problem?
I have read many posts on acclimation, and I do acclimate everything, I don’t think this is an issue as the critters seem to go a while before they die.
At this point all my numbers from my tests look good nitrate < 15 salinity 1.025 (LFS told me to use this number) I use a refractometer for this. Others numbers are where they need to be, I don’t test copper or phosphate, I test just the usual. The main reason or question for this post is to see what I’m doing wrong – I don’t think it should be this complicated. At this point I would like to stabilize the tank, get the coral healthy and add some snails back, make sure they act normal and take it form there.
What should I do?

38 gal, octopus skimmer, 1200 Maxi-Jet, 2 x 30 t5, live rock/sand
Life: 2 Clown, 1 Lemon Peel, snails
Corals: plain zoas

 

Welcome to 3Reef

I would have your fish store test your water for copper. If your fish are fine but all your inverts die, I suspect you have too much of it.

 

Ill do that tomorrow, remember the certh snails are fine, and I think the inverts died due to the high nitrate chain reaction of the snails dying. I'm not even sure how i would get copper in my water as i use roi and have newer house with plastic instead of copper pipes.

 

Doesn't seem feasible for one little astrea to bring up your ammonia that much. I have hermits in my tank for just such an occasion.

 

I agree, - at this point it does seem like there has got to be something wrong with my water. I'm just not sure what.

 

Have you checked the TDS of your RODI unit's output? Maybe the DI resin is used up and is letting some stuff through or something?

Also have you calibrated your refractometer recently?

Aren't some inverts sensitive to stray current too? Maybe find a way to check if some of your equipment is leaking electrical current?

How much live rock do you have? One snail dying shouldn't cause a problem if you have enough rock/filtration.

Have you checked your ph/alkalinity?

Just some ideas, good luck.

 

Did you buy the tank, and all of the equipment, brand new? There are many ways copper can enter the system
Also, do you have a grounding probe? Inverts are very sensitive to stray voltage.

 

Have you checked the TDS of your RODI unit's output?
I'm not exactly sure how to check the TDS - ill look into it. My wife did notice the water smelling, then i changed the filters, and it went away. This could very well be the problem.
calibrated your refractometer recently?
Just did this.
do you have a grounding probe
No - probe, other certh snails are ok, wouldn't they die also
Did you buy the tank, and all of the equipment, brand new?
The tank was my old freshwater tank, I didn't use RODI water, the equipment is all new
How much live rock do you have?
I could add some more, I will add some more. I have around a total of 15 pounds
Have you checked your ph/alkalinity?
I will do this tonight - it has been ok however i dont check it to often,

Thanks for all the replies so far, it seem there are many things in my water that need to be checked out, Currently my suspicion is my filters on the RODI was run to long (I was going to change them 6mo, however after the smell I switched to 3mo), Any other suggestions are welcome as I don't want to give up on this hobby and want to succeed, It cant be that complicated?

 

Purchased the TDS monitor tonight, Exactly what ppm will i be looking for when its time to replace the filters? Then would you replace all of them, or all but the TFC membrane?
Also I checked the salinity its at 1.023 - ill slowly bring that up through water exchanges.
I'm still leaning towards the filters in the RODI wearing out.

 

Got back from LFS and all numbers are good except nitrates are at 15. No copper no phosphate high calcium.