FYI. You mentioned 1ft can be multiplied by 3.3 to get metres, so 100ft is 330m. But it’s the other way round. 😜

In reply to Krivi K ………… The foam cubes don’t work as well as the K1 type media. So I don’t recommend them.

what are your thoughts on swisstropical’s aqua media?

its designed to be used in fluidized beds similar to K1, is there any benefit to this as compared to traditional static sponge filtration?

Poret®aqua Media Shop – SWISSTROPICALS

In reply to Kim …………. Your calculations are correct. Welcome to why the fluidized bed sump is so well received by all who use them.

I’ve been in the hobby forever, but just came across your site. Wow, what a great resource. I wish I’d found it sooner. I can’t believe some of the myths I’ve accepted as facts.

I’m going to replace my 125 gallon tank two cannister filters with a UG filter + a fluidized K1 sump. I’ve done the calcs for the sump to see if it will get me over the 100 sq ft of media / lb of fish. My calcs show the efficiency of the fluidized K1 to be so high that I’m worried I made a mistake.

vol of sump compartment (water + K1 @ 60%) will be 2.7 cu ft = (30″ x 12″ x 13″) / 1,728
effective media surface area will be 1,463 sq ft = 2.7 cu ft sump vol x 540 from effective surface area chart
lbs of fish at 100 sq ft of media / lb will be 14.6 = 1,463 / 100

That fish weight just seems so high. Have I made a calc error or does that just reflect the efficiency of a fluidized K1 sump?

Thanks, Kim

In reply to Yecheng ……………. Sounds like you are doing everything right. I’d just be real cautious about overfeeding.

In reply to Charles Cheuk ……… One gram of protein produces one third gram of nitric acid, IRREGARDLESS OF THE MEDIA DOING THE OXIDATION OF AMMONIA TO NITRIC ACID. But ammonia poisoning is another matter. You need to cycle the tank with a fish in cycle in order to get it going in the right direction. Just cut way back on the feeding for awhile. And, yes, add a bag of crushed coral to the filter.

Ever since I changed the filter media, they started showing signs like darker scales, losing their previous shine, and some became less active. We know Corydoras are usually very lively. I observed that within about a week of noticing the lethargy, the fish would die.

I believe the first reason for the pH crash was that I replaced all the mineral filter media at once, without doing it gradually in stages. At the time, I foolishly thought that mineral media probably doesn’t host as much beneficial bacteria compared to the filter sponge, and as long as I didn’t change the sponge, the nitrification cycle wouldn’t be greatly affected. So, I replaced all the mineral media I was using with sponge.

Afterwards, with the same feeding routine, the nitrifying bacteria in the tank were insufficient. This likely led to a large colonization of heterotrophic bacteria on the newly added sponge, causing the biofiltration efficiency to drop and instead producing a lot of acid. Of course, this is my speculation; my chemistry knowledge is very weak, and I’m mostly guessing.

The second reason is that, apart from the Matten filter (which is one large, thick 5cm piece of foam), I used too little sponge in the overhead filter. I left a lot of space for water flow because I thought at the time that seemingly more water flow would be beneficial for faster establishment of the nitrification system. So, it’s possible I ended up with insufficient total filter media volume, as that large Matten filter foam surrounding the water pump likely needed more time to mature, resulting in an insufficient amount of media actively participating in filtration.

Thus, under high stocking density, insufficient filter media can lead to excess nutrients and water acidification. The above is just my hypothesis. I still crave your professional answer and help. I think it was my rushed, complete replacement of the tank’s filter media that caused me to lose my old buddies, not necessarily the switch to sponge media itself. But until I get your insight, I feel that sponges potentially harboring a lot of organic matter might be the main cause of the pH crash.

Also, I’d like to ask: if the population of autotrophic bacteria was very large and could form robust biofilms, would the situation have been different?

Finally, most of the fish I keep are South American species, and I usually have driftwood in the tank, which makes the water slightly acidic. Should I place a bag of crushed coral in the filter to stabilize the pH long-term, or is this unnecessary if the biofiltration system is very powerful?

Thank you once again. I look forward to your reply.

Reply to Charles ……. ALL filter media accumulate nitrate at equal rates. Add a bag of crushed coral to the filter to buffer the water to a better pH. And close down the holes in the foam. It is much better to have slow flow through all the foam rather than rapid flow though only part of the foam.