Dead Spots = Death?

[womquat]

Hi - I'm new to the site, which was recommended by my brother-in-law. I have a curious problem with my wife's marine tank. It's a 23 gallon flat-back hex with twin-plate undergravels pumped by Hagen powerheads. I also run a Fluval with Bio ChemZorb, Ex-Silicate, and PhosZorb. Bottom section runs Fluval "Bio Macs" and top holds the sponge.

The substrate is Phillipine crushed coral and I keep the salinity at 1.018. There is no ammonia, no nitrites, and low nitrates. All seems fine from that perspective.

A while back I decided to do a thorough gravel cleaning with a siphon gravel vac, and it wiped out the tank - everything. I let the tank run for two weeks with no critters and then introduced a "test molly". All went well and I started adding more fish. Recently I added a yellow head jawfish (one of my wife's favorites) and it did great for a couple of days. It wasn't until she dug herself a burrow under a head of blue coral that things went south. She started breathing very heavily and within a day was dead.

I know from the past that dead spots often occur under "decorations". However, the gravel vacuuming seemed to kick up the same problem. Is it possible that there isn't enough flow through the gravel and this is causing anerobic activity and thus problems with gas buildup? Should I increase the flow through the power heads? Do you think this is what caused the jawfish to die?

Any help, hints, and suggestions will be greatly appreciated!

 

[alleykat81]

IMO you shouldn't be using an under gravel filter for saltwater. Your salinity seems to be too low, also. I keep mine around 1.023. You need to be thoroughly checking your water params. I have a shallow sand bed and I only stir up a small portion of the top layer. I know vacuuming up the entire bed is a no-no.

 

[womquat]

Hi - thanks for your reply. I keep the salinity low on purpose because it tends to keep the parasite possibilities at bay. I only keep fish in that tank and we always had pretty good luck doing this at the store I worked at. Red Sea fish we kept higher, as did we inverts like anemones.

I've debated whether to get rid of the undergravels. I hadn't had problems with them in this tank in the past. I may look to invest in some other outside biological form of filtration. I have a birthday coming up soon and I never know what to ask for!