Using an extra canister filter empty - what's the risk

[kendrid]

I am setting up a 20 gallon tall in about a month. I have a SunSun canister filter on my 90 gallon discus tank and I'd estimate its volume at 3 gallons. I am going to check it tonight when I do a water change.

I know people say canisters can cause nitrate and phosphate issues. What if the canister is empty except for carbon/purgien/etc? If the volume really is 3 gallons to do a water change all I would need to do is disconnect it, empty and clean, refill, done. No pumps, no hoses. Another advantage is that the canister would have a UV light. The flow is 525 GPH (supposedly) so the return would act as a small powerhead.

I am going to have a one gallon HOB refugium and put my heater and cheato in.

[Fish_wiz2]

You will be fine, the reason for the nitrate and phosphate issues is the use of the included sponges and biomedia without regular maintenance. What you described it exactly what a media reactor does and is perfect. Wiz.

[kissman]

It will be fine as long as you keep it clean from detritus settleing on bottom. UV lights do have there pros and cons, they can help with disease and algae, but they can also kill the good bacteria you need

[kendrid]

Thanks for the replies. I change 50 gallons in my discus tank every week. I have that tank plumbed into my RODI water storage unit and house drain so doing water changes takes 15 minutes. My plan is do empty the canister while the discus tank is draining/filling. I will wipe it out, check the Purifen, etc. I've been doing it for the discus for two years so adding another tank to clean isn't a big deal. I enjoy it.

Here is my water change setup: http://m.youtube.com/watch?v=2vbeknk-L_4
As you can see I basically have the plumbing of a sump setup. I would do a sump for the 20 gallon but I have a nice stand and really not any room for a 10 gallon sump.
The canister in that video is what I am thinking about using on the 20g. I need to see how it will fit under my 20g stand later today when I clean it and determine the volume of water it holds.

I have an extra 10g so if I could get it to fit somewhere I'd make a sump. Decisions... The filter is $100 plus $40 for the HOB fuge and pump form it. To convert my 10g would probably cost the same or maybe less. I need to find a spot for it...