Canister Filters

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Registered Member
Jul 15, 2020
I used to have a 55 gallon fresh water aquarium back in the late 90's using undergravel filters. Everything was good for about 6 months when I moved the tank into a room with a lot of sunlight (although not direct sunlight) and I started to get an algae problem and nothing I did could get rid of it. It almost required daily water changes to just see into the tank. Then someone suggest I get an external canister filter and use crushed oyster shells - the stuff you purchase at a pool shop. The results were amazing! The tank was crystal clear, no more algae. Something with the combination of the filter and the powder made for a very effective filter. I ran the filter 24/7 but would only add the powder and run for about 6 hours. Then I just washed out the filter to remove the powder and all the junk and fine particles that it had collected. I replaced the filter every month. The fish seemed to thrive and were very healthy!

After a few years, life happened and I got rid of the tank and all of the equipment. Now I have a 50 gallon and moved to a place where the room is flooded with light. And algae is once again a problem. I have tried tablets, daily water changes.... even emptied the tank completely and tried washing everything. I am pretty sure I just need to go back to using a canister filter with the crushed oyster shells again. But here is my question/obstacle. The old canister filters had filters that were similar to what you find in those pool filters that you replaced. Long, blue ends, and white. You put a little of the powder in the intake hose and it did its job. I am not sure I understand the new filtration of canister filters and asking someone at PetSmart or other local pet stores.... they just suggest I use tablets like "Algae No More" or give me that "deer lost in the headlights" look.

Anyone familiar with what I am talking about from the past and can give me any guidance on what to purchase that would work with the crushed oyster shells?


AC Members
Jun 28, 2006
SF Bay area, CA
I think you probably had a Diatom filter. We had 1 back in the early 80s, a Vortex 360? I could never get it charged but my husband did. We only used it to "polish" the water not all the time. It was when we had under gravel filters too & any time we rearranged decor it would stir "crap" into the water column.

We don't use UGF or a Vortex these days but my husband misses them both, lol. (he's stuck in that era as far as tanks go). I think they may still sell Vortex filters...

Since algae is an all the time problem my first thought is less time with the tank lights on since your room is so bright. I use a UV filter for temporary green water or a Aqua Clear Quick filter for floaty stuff (algae & "crud"). It's a powerhead with a filter & fine media filter bag that attaches to it (clogs fairly fast). I don't really think either is a long term answer for you, they take up a lot of tank space.

Some canisters have built in UV but I've never tried 1. Another option is very fine filter media like floss to remove the algae. With most canisters & some HOBs you can add media layers however you want including crushed coral or oyster shells in a fine media bag, but the fine floss will clog fast. Look at an easy to clean filter since you'll be doing it often.


Global Moderator
Staff member
Jan 11, 2013
West Falls NY
Real Name
Will the tank be up against or very near windows?

Just to add to the above advice, you should be able to control algae in the water column with water changes, light feeding, feeding quality foods and the occasional scraping of the interior glass as needed.

I have a 75gal right up against a large southern facing window. The tank does have a vinyl background on the back of the exterior, but the sides and top get flooded with light all day. I never have an issue aside from having to wipe the insides of the glass from time to time. This tank also has a 48" cheap LED strip light on a timer for about 8hrs/day.