Ok my tank is a 10 gallon with 2 pairs of clowns (this is temporary until I get my 20 up and running), a pair of breeding coral banded shrimp, a 2 head frogspwan (so to be 3), an acan with 5 heads, 2 zooanthids frags, a huge coral colony the size of a softball (not sure what it is), and just bought a ricodiea yesterday. I use a hang on the back filter with a bio balls and filter cartridge not sure if it has carbon but it probably does. My lights are on for 12 hours. And I don't do water changes at all which is ironic because I live a block away from the Atlantic.
lol.. man, I'd take advantage of that ocean if I were you!! I've always thought how cool it'd be to live on the ocean, and pipe in real ocean water ... I'd have a HUGE system.
How long has this tank been up? Are we seeing NH3 because we are still in the initial cycle, maybe? What you explain is not that much bio load... How much live rock or dry rock (where'd you get it)? substrate/sand? How much do you feed? How much flow do you have?
Do you know what the model of your HOB filter is so I can look up exactly what it is? Any GAC/carbon filter by this point at 150+ NO3 has probably long been used up.
@ 10 gallons, or even 20 it is very easy to do 10 or 20% water change every couple weeks (or even weekly), and you will see a difference in your system. Get a 5gal bucket, 5 ft of ~1/2" tubing, and a 5 gal water jug. 1) start by SLOWLY matching your salinity in your tank to the ocean (your water source) over the period of several days if there is any difference to start with. Once you match salinity to that of your water source, your goal is to keep it there (hopefully with daily fresh water additions of RO/DI or disitilled water - not conditioned tap water). 2) fill up your 5 gal water jug with ocean water and drop a heater in for several hours to match tank temperature. 3) use a sharpie to mark gallon measurements in your 5 gallon bucket so you know how much is in the bucket at any point in time. 4) syphon out desired amount of water from your tank into the 5 gallon bucket. 5) Replace water with fresh sea water which should now match temperature and salinity. You can gently dump it into your tank over a piece of rock, or set up a bucket above the tank, somehow, and use some 1/4" airline or something to syphon it into the tank - just be careful not to overflow! If I syphoned - I'd probably get a funnel and a couple 1gal water jugs to syphon from so I didn't overflow my tank (because I'm forgetful)
If you have a lot of GHA, I'd probably pull out what you can regularly. During your syphoning for water changes you might also be able to suck out some GHA and or detritus buildup on and in between rocks or sand. Try not to let detritus sit in your system - as this desolves and turns into NO3 and PO4. Also note GHA traps detritus. Be patient with the GHA... it takes a long time to go away even after nutrients are very low.
How were you planning to introduce a refugium?
