Canister Filters - Why Not
I have a 55g tank, 70lb live rock, 2-3" live rock bed.
I have T5 lighting with 2 bulbs, 1 blue, 1 natural.
2 power heads giving out 250gph
AquaC Remora Pro Protein Skimmer
I also have a Fluval 305 Cannister Filter.
My tank is 3 weeks old, the live rock was cured already from the LFS. Parameters are:
Salinity: 1.023-1024, Temp 81, pH 8.3-8.4, Ammon:0, Nitrite:0, Calcium:400ppm, kH:180, Nitrates 10-15ppm, occasionally upto 20ppm.
My aim is to run a community reef tank.
I already have a cycling 10gal quarantine tank elsewhere in the house as I've read that this will help ensure success and assist hospitalising and acclimating livestock.
I've seen many posts to say to scrap the use of the fluval or just use it empty of all media. Apparently just a trap for organic material unless cleaned weekly.
Quite a few web sites promote the use of these types of cannister filters to house filter media such as carbon, biological filter (E.g. Fluval Bio-Max), phosphates reduces and nitrate reduces. Indeed, the media trays are so flexible that you can tailor the media in use for what you need to help control.
Can I ask why a marine tank shouldn't bother with this type or any type of cannister filter? I assumed and read around that the additional mechanical, biological and chemical filtration as well as the live rock and sand would assist in keeping water parameters in check, minimize ammonia and nitrite and assist with reducing phosphates and nitrates with the correct filter media when used in conjunction with regular water changes.
So, lets take the "benefits" and look at them, starting with mechanical filtration. Mechanical filtration in general is almost never used on a reef environment, because the filter pads trap organic acids, causing them to be processed biologically. This biological processing adds Nitrates to the water, and as an extra benefit, Phosphates. It is better to allow these organic compounds to enter the protein skimmer and be removed directly from the water, rather than processed biologically. (Note: cleaning the filter pads DAILY can prevent this to some degree)
The next benefit often named is biological filtration. After reading the paragraph above, it becomes clear that we do not want any unnatural form of biological filtration on a marine aquarium. The goal in a marine system is to reduce Nitrates and stabilize alkalinity & calcium. The addition of any biological filter media is in direct conflict with this goal. Biological filters add Nitrate to the water, and the process of organic breakdown depletes carbonates. It is far more effective to allow the live rock and sand to do what it does naturally, which is to process organic waste with an end result of nitrogen gas, which leaves the system naturally.
The use of chemical filtration inside a canister is a little less harmful, but any chemical filter media which has forced flow water will become biologically active in very short time, resulting in biological filtration and the negative effects associated with this. The easiest and most effective method of chemical filtration is to place a bag of carbon in your sump. Carbon will effectively remove water tinting acids passively... forced flow is not needed. You could make an argument for using a phosphate sponge periodically, but not for continuous use inside a canister, due to the negative discussed above.
The need for ammonia or nitrite control on a marine system with adequate live rock does not exist. Again, all forms of unnatural biological filtration need to be eliminated.
The only benefit of a canister filter I can come up with is one that you have probably not heard about. This is when the diatom filter cartridge is used to spot polish the water. Some pathogens are large enough that a diatom filter can remove them, helping to sterilize the water in a way similar to a UV Sterilizer. But this method would be better used on the Quarantine tank, or as a spot polish after scrapping algae on the display.
So, we have negatives of: phosphate buildup, nitrate buildup, and carbonate depletion.
We have positives of: possible pathogen removal when used with a diatom filter.
Well, that really answers quite a lot and in detail and I'm very grateful. Just learning about the processes involved in the system of keeping a marine tank is actually part of my fasination with the subject. Many areas of literature blindly discuss biological, chemical and mechanical filtration without really discussing in detail about the various appliances available for the aquarist and the pros and cons.
In the last week I started to see and increase in the phosphates in my tank, up to 0.5ppm and included a phosphate remover from Hagen (clearmax) to remove them. I've also always been trying to get my nitrates below around 10ppm with water changes, sometimes up to 20% of the volume. I didn't really consider, or know, that part of my problem could be the media in the cannister filter. I know my water is sound from the tap as I've tested it before using it and everything is zero. I'm confident in this as I installed a home filtration system last year by RainSoft to deal with general poorer water quality here in Houston. I decided to test my water, both fresh and then 2 day old saltwater in a bucket and everything is zero. FYI I use RedSea Salt from Oceanic.
I'll change out the filter media and just leave all the baskets empty and simply use the cannister as an additional water source. Unfortunately I don't have room under my tank stand for a sump to add an carbon as there is only 13 - 16" of clearance and I've yet to be convinced of an overflow system for providing water to a sump.Could using a bag of carbon in the bottom of the cannister be effective as you mentioned for using one in a sump? If the other media is removed then the flow isn't quite as forced?
Thanks for the advice. I'll make a note of water properties before I remove the media and then on regular intervals. It might be quite interesting and learning for me.
I suspect that placing a bag of carbon in a hang on filter would prove easier. I'm afraid the suction from the canister would draw the bag and clog the canister.
On the subject of phosphates, keep in mind that your phosphate test only tells you the amount of phosphate that is accumulating beyond that which is being utilized by algae within your aquarium. Even a test result of zero does not imply that phosphates are not being introduced. It only means that phosphates are being utilized by the algae faster than they are being introduced.
So if I'm understanding everything right the following is going to develop:
The first stage of my cannister is foam pad. This will trap larger detritus but these will start to break down releasing additional nitrate into the system over and above any breakdown directly in the tank.
My next two stages, carbon then bio-max media will eventually become active and further lead to additional nitrate introduction to the tank. Obviously the two bags of phosphate remover will additionally become active and do the same.
So in a marine tank you are simply only suggesting power heads and a good protein skimmer like the AquaC Remora Pro that I have. The skimmer will handle all the mechanical filtration and permanently remove organic waste from the tank.
The biological filtration, breakdown of ammonia to nitrite to nitrate then nitrogen gas will be handled by the volume of live rock and live sand.
Sounds like an interesting and logical process. The only thing I'm missing is the ability to include a sump in my setup where I could introduce carbon without the forced flow.
honestly i dont think an aqua c is enough for a 55 but thats my opinion. i never was a fan of hang on skimmers anyways.
enough live rock, sand, flow, a quality skimmer, occasional small water change, good feeding patterns and pre-rinsing foods, a sump is always nice w/ a refugium and thats all you should need on a marine tank.
Ok, so yesterday I took the plunge and did some quite radical changes, at least in my eyes. First I removed the Fluval 305 canister filter and cleaned it all out completely of media and washed inside and the media trays. I put them back empty so flow was still directed through the canister to at least give me the 200gph flow and to prevent any chance of dead water at the bottom of the canister.
I also made a quite large water change - 30% to be exact. The reason for this was because on Sunday my home AC failed. In Texas at the moment we are getting around 98F every day. The AC was not fixed until Tuesday and my tank was running around 89F for two days. I took a precaution, perhaps unnecessary, to do this change after my tank water had returned slowly to normal temperature. I didn't want to shock the skunk cleaner, 4 hermits & 4 snails in the tank.
I took some reading before the change in water, amm:0, Nitrite:0, Nitrate:10-15ppm, Phospate: 0.5ppm,pH:8.4. I'll now see what the impact is over the next week in the levels.
I also did a measure of my live sand and I'm running at an average of 3". It has been in for just over 3 weeks. Is it OK to buy some more and add it to my current sand base? If so, and I assume it is - I buy Carib-Sea live sand that ships wet - should I mix it into the current sand base or just place it ontop?
OK an update after 1 week.
On Saturday I bought a 20lb bag of Carib-Sea live sand, the same as I already had in the tank to increase my depth of live sand from around 3" to around 5".
I tested my water last night, 1 week after empting out the canister filter and just running it empty and doing the 30% water change. I can't believe the change in the week. No more additional algae growth on the back glass or additional on the live rock. My water test numbers are better than they have ever been:
Ammonia, Nitrite, Nitrate, Phosphorous all 0. Great Calcium (400ppm) and Alkalinity(180ppm) numbers, pH around 8.3-8.4, Density:1.023.
I have 2 cleaner shrimp and 10 hermit crabs all living the high life in there. My two Clown Fish in the quarantine tank will get moved on the weekend into the display tank.
I'm a convert to this no additional filtering other than the LR and LS. Thanks for the explanation. I'm not one to believe everything at face value and want to confirm things for myself.
I can testify from first hand experience. The difference is amazing. It only takes a couple of weeks without mechanical filtration for the changes to be noticeable.
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