Kevin M – Couer D’Alene

Kevin is clearly a dedicated DIY enthusiast. He got a 5 gallon Marineland tank for his son’s goldfish that was outgrowing the fish bowl. He wanted to tune it up a bit so in Feb 2021 he got a hold of us to bounce some ideas off us.

Hello, I have a 5 gallon Marineland portrait style aquarium and am looking to modify the existing filter. It has activated charcoal filters and I’m ditching those. My question is, do you have a recommendation for filter media? I was looking at biohome plus, but then saw the biogravel. Would the biogravel be a better material due to limited filter space? Thank you for your time and any information you could provide.

My response:

Looks like a cool little tank. Yes, I would suggest using BioGravel. You only need 500 grams for that size tank. It looks like there may be enough space to hold that much.

500 grams only requires 38 cu in of space. In the picture I saw, it’s not clear exactly how the water flows through the filter section.

There appears to be lots of room in the Filter Box, but I’m not sure how the Cartridge Carrier relates to this. It looks like they use a single block of foam for mechanical filtration with a carbon cartridge behind it. I can’t tell where the water goes from there.

it looks like water could go down from the Foam Filter. That doesn’t make much sense since it would bypass the carbon.

If there is a path for the water to go down into the lower portion of the Cartridge Carrier from the space where the Carbon Cartridge is located and if you could block the path at the front of the Cartridge Carrier, you could probably fit enough BioGravel into the bottom of the Cartridge Carrier and you could improve the mechanical filtration by using a 6 1/2″ Foam Filter Set.

Hope that helps. Let me know if you have any questions. It would be helpful to get more info on how the water flows.

It sounds like you’re up for modifying it. It looks like the tank is about 15″ high and I expect the filter housing must be about that tall as well.

If you could plug the existing inlet and then cut some slots about 1/8″ wide and 1 1/2″ tall. Make the slot pattern almost as wide as the filter housing (Cartridge Carrier).

Kevin came back with some more info:

It’s an interesting filter setup, and seems to need a little modification. The right ride cartridge area has the carbon filter on top and a sponge on the bottom. In your image where you ask about room for media is where the sponge sits.

The inlet is about halfway down on the right ride of the tank and the cartridge carrier stops about there. I imagine I could block the inlet and make a new one at the bottom of this section, then modify it or rebuild the cartridge carrier, changing the whole right side into a more efficient filter.

The water in the back section where the power head draws from gets a little stagnant so I’ll have to do something about that. I’ve wanted to set up an aquarium for years and never really got around to it. I got this kit for my 4 year old for Christmas so his monster common goldfish could move out of his bowl.

Since Christmas I’ve been researching and learning a ton about the hobby. After I make the few mods to this kit, I’ll probably set up my own tank. In researching, I found this link about this tank and some mods. I’m going to be adding a heater, getting rid of the carbon filter cartridges for the biogravel and putting a couple holes in the tube to solve the stagnation problem.

Every time I look something up or watch a new video, I want to run out and buy a tank and build something from the ground up lol. I’m sure in the next few days I’ll be placing an order to finish modifying my son’s tank first, before I jump into another project. Thanks for your input on which filter media to use.

Kevin provided a link to a video which provided more info on how the tank and filtration worked. That gave me some more ideas:

That video was very useful. I understand a lot better how it works now. I just found a photo that shows the filter inlet location. Unfortunately, it’s in about the worst place possible. It’s too high to clean the bottom effectively and too low to skim the surface.

It sounds like you’re up for modifying it. It looks like the tank is about 15″ high and I expect the filter housing must be about that tall as well.

If you could plug the existing inlet and then cut some slots about 1/8″ wide and 1 1/2″ tall. Make the slot pattern almost as wide as the filter housing (Cartridge Carrier).

You could then get a 6 1/2″ Foam Filter Set and cut two Coarse Filters to fit into the bottom of the filter housing. This should cover the slots. Then cut one or two Medium Filters to fit on top of the Coarse Filters and finally a Fine Filter to go on top.

This then leaves the top section for BioGravel similar to what was shown in the video. He then suggested cutting some holes in the output tube. He was talking about a betta tank and was after minimal flow.

Your goldfish probably would like a little more current and is probably dirtier than his little betta. I’m thinking you might solve this problem by making your water changes there. That is removing some water from the tank and then adding it back through that section in the back.

I’ve recently purchased a similar tank and noticed the same problem. That’s what I’m going to try. If that doesn’t work sufficiently, you could always cut the diamond slots he described.

He drilled holes all the way through. Since the pump sits at the far left end, I’d cut the slots on the side of the tube  pointing at the center of the area.

Kevin came back with some more info:

Yeah, I thought the inlet would have been better lower, which is how I was thinking about modding it. I might just buy another version of this tank to mess around with, just in case I screw up. Good idea about water changes and pouring water back into the pump area.

I didn’t want to make as many holes as in the video but think with a heater in there, a couple would be helpful for the reasons he stated. I was thinking maybe one or two holes in the right side of tube, slightly directional to circulate the water downward in the chamber without reducing too much flow.

I have the pump set at half power, as Wally seemed a little weirded out by his newfound current when transferred from his bowl. Now though, he swims to the left side, faces me and drifts sideways across the tank. I don’t think increasing the flow would bother him now. I gotta say, this fish definitely has some personality.

A hobby of mine in recent years has been making silicone molds and things from plastic so, maybe I’ll design a new filter cartridge that goes the full height of the tank for building the new filter. So yeah, I’ll probably be buying another one of these kits to fiddle around with someday for sure. Thanks for advice and specs for building a better filter. 

My reply:

If you want to play around with another tank, you might consider the UN Systems tank which I think might be a little more flexible. Here’s the one I got recently.

These photos show it with a HOB Canister filter installed. I recently removed that and added about 700 grams of BioGravel in the center filter section, which would hold a lot more. I just added one Media Bag. You could probably pile two or three in there, although I don’t think you’d need that much. The tank only hold 7 gallons in the livestock section.

It comes with a large block of Fine Foam in the first inlet section. That promptly plugged up. I cut a strip about 1″ thick off and added my Coarse and Medium Foams on top of it.

The water exists at the bottom of the Inlet section into the middle section which is what I would and am using for bio media.  Water overflows from there into the return section which comes with a pump which turns out to be quite noisy. I’ll be replacing that, but probably doesn’t affect all of them.

A couple of weeks later I heard from Kevin again:

I’ve finally gotten around to modding my tank, it’s been a busy month. I have 2 last questions to ask you before ordering media. The space in the sump compartment is 1 7/8″ deep, would you recommend regular bio-gravel or the larger super bio-gravel for my filter bag?

And my second question is, would it harm the powerhead at all with the gravel bag resting partially on it? Or, should I build a small shelf of sorts for the bag to sit on? I imagine I could cut a small piece of foam filter that would support the weight of the filter bag, it’d just add an extra little step during maintenance.

My response:

I’d stick with the BioGravel since your filter area is fairly small. As for letting the Media Bag to rest on the Power Head/Pump it probably depends on which kind you have.

If you are referring to a pump similar to this, I don’t see any problem as long as the intake area is not covered.

If it is actually a Power Head that might look like this, then it might be better to provide some sort of support.

Hope that helps. Please let me know how it turns out.

Well I didn’t hear anything from Kevin until this past July, when he had another project in mind when the goldfish needed more room.

It’s Kevin again, you might remember me from over a year ago, perhaps not. I needed your opinion on modifying a 5 gallon tank filter by adding BioGravel to the sump filter. Anyway, I have a new project that I’m working on as my son’s goldfish needs a little more swimming room. I’m upgrading him to a 10 gallon tank.

My question again is about which media would best suit the size of my container. I modified a sponge-filter by adding a canister to it for bio-media. I used a jar that’s 4″ tall by 2 1/2″ wide to contain the gravel.

Looking at the SuperBioGravel, it seems to be the best size but was wondering if Biohome Mini would be a better choice, as it would fit in the container as well? Also, 2nd question. Since I’m using a canister on top of a sponge filter, will the air bubbles moving around the bio-media kill the denitrifying bacteria inside it or is it deep enough inside to be safe? Thanks again!

So another interesting project to work on with Kevin. Here was my two cents”

I’m not sure how you plan to connect the filters so the flow from the sponge filter goes through the canister. I’d agree SuperBioGravel would work best. It gives you the most bang for the buck.

Assuming the canister is round it would only hold about 150 grams which isn’t enough to do much good for anything. The 10 gallon tank would require about 700 grams.

Good question about the air. I have heavy aeration flowing through SuperBioGravel media in my koi pond filters. I don’t get any nitrate reduction, but that may be because there isn’t enough volume in my filters for that.

Sorry I don’t have better information. Hope this helps a bit. Hope you can find a larger container. Probably better to use a small pump for flow instead of the air lift.

Kevin got right back to me with more info:

Thanks for the fast response. To connect the filters, I drilled a hole in the jar lid that fits over the top ring of the sponge assembly, maybe 3/4″.

Then, I drilled an airline hole through the center of the bottom of the jar, and a few holes around the rim of the bottom of the jar. Finally, I ran the airline through the jar (and media).

It essentially turns the whole inverted jar into an airlift tube, but instead of the lift tube, it’s a bio-media jar. I can definitely find a larger jar for bio-media.

The flow seems to be decent. I already had the air pump and sponge filters on hand so I figured I’d see what I could do about making them better.

I attached a picture if you’re curious about the filter setup. I also just weighed what I have in there, the small BioGravel, and there’s 315g of it. No need to apologize for the information you provided, anything new I can learn is a excellent. Thanks again!

Didn’t have much to add to that:

Pretty cool filter. If you can scale that up a little over 2x, it might work pretty slick.

In October, 22 got a final report on Wally and Bob’s tank:

Tank has been cycled, Wally the Goldfish was added about a month ago and Bob the Snail was transferred a couple days ago after I was sure there was enough algae for him to munch on. I’ve attached a couple pictures and a video so you can see the filter setup.

I just tested water and my nitrate and nitrite levels are in the safe zone and Wally is a pretty heavy pooper. The larger sized biomedia is great because it doesn’t fall through the connecting hole in my jar when I disassemble it for cleaning. But, I might end up making a small future modification and add a piece of mesh or something over the hole so I can fill in the gaps with the smaller media I have. Have a great day!