Pond / Filtration decisions.....

[Andy41]

Hi Guys,

Everyone here has been giving me good advice over the last few months, and the time has come to get your feedback on my idea for the pond...

The pond has been dug out, and is approximately 14000 galls (52000 litres) in volume. The pond is a figure of 8 shape, with two large planting areas at the top and bottom of the 8, and i'm planning on building a log bridge over the middle later on. One of the planting areas will also be divided between planting and a bog area.

I'm counting on the bog / plants to do about 40% of the filtration for me in order to reduce the biofilter to a reasonable size. I'm calculating everything with a turn over rate of once every 4 hours, so 6 times a day. This gives me a flow of about 4000 gph (15,000 lph). I'm going to use 2x 55 gal skippy filters in series as the biofilter and a vertex to seperate out the solids. With this flow rate that'll give me a combined dwell time of 8 minutes in the biofilters.

The setup i'm thinking of at the moment is :

retro-drain - pump - uv filter - vertex - bio 1 - bio 2 ----- return 1 / bog.

For the pipe i was going to use 2" PVC upto the vertex, and then 3" after that. The feed to the return / bog is then split using 2" hose.

The pump, uv, vertex and biofilters will be housed in a wooden enclosure next to the bog area.

Can anyone see any obvious problems with this setup? Have i forgotten anything?

I should mention that the pond will only be holding goldfish.... i have about 4 large fish (20cm+) and about 90 smaller fish (5cm) at the moment.

cheers,

Andy

 

[vertigo72]

Hey, I got a very similar setup. Same size pond, relying on a few 100 iris plants and (for now) 3 DIY barrels. A few semi random thoughts;

1) aeration. You dont mention a fountain or waterfall, nor airpump. You will want one of those at least. I got a powerful (160L/min) airpump that I use to drive ~3 airstones in each biofilter (improves their working) and a large air disc in the pond. Also useful to keep an area ice free in winter, and if you put a big disc in the middle, it drives floating debris to the sides, towards your....

2) skimmer? A pond that large, you definitely want some surface skimming.

3) Im not sure how much biofiltration youd need for 90 goldfish, but I assume its tangible. You may have seen my reply to fishin4cars where I made an educated guess for amount of biomedia per kg of koi, I guess it would be only slightly less for goldfish (per kg of fish). I just googled and found a goldfish can grow up to 23 inch and weigh up to 4.5 Kg. Up to 2 Kg being more the norm. Times 90x is a lot. I calculated 2 55 gallon biofilters would suffice for ~15 Kg worth of koi. So Im a bit worried there, unless you plan on keeping your population smaller once these fish mature, or you have a variety that doesnt grow that big.

4) Depending how big it is, one vortex is likely not going to be enough. Its not enough for my pond, though I must say my pond is almost in the middle of a forest (trees all around). Also, when feeding it 15K liter per hour, you need a big enough vortex or the water will flow too fast and not have time to settle. Im pumping about 6-7000L/h in to a 55 gallon vortex, and its a bit too much really. With brushes it works okay, without brushes, dirt doesnt settle. Go for a ~400 liter model, or use more than one vortex in parallel. Alternatively, Id look in to a sieve.

 

[Andy41]

Hi Vertigo,

1. True, i forgot to mention this. I was planning on airstones in the biofilters, but hadn't thought about the pond.... an air disc is a good idea.

2. I also hadn't thought about a skimmer.... how have you plumbed this into the system?

3. I'm using one 55 gal biofilter / waterfall at the moment for the fish in a 6000 litre pond, and that works well. So i'm hoping that 2x of those filters, plus a whole bunch of plants, will be ok for the new pond.

4. Good point about the vertex..... i hadn't considered how long the settling time would be. A sieve is also an idea, but this is going to clog up quite quickly i suppose.... If i need two vertexs then i'm going to have to make the filter enclosure a bit bigger!

cheers,

Andy.

 

[vertigo72]

2. I also hadn't thought about a skimmer.... how have you plumbed this into the system?

Simple, I pump from the skimmer to the filter, where its combined with the flow of the bottom pump. Note I dont actually have a proper skimmer, Im stll breaking my head over how to build one properly in my concrete pond, for now I just have a container thats a few mm below the water surface with a 8000L/h pump in it. Ugly as sin but it sure works.

3. I'm using one 55 gal biofilter / waterfall at the moment for the fish in a 6000 litre pond, and that works well. So i'm hoping that 2x of those filters, plus a whole bunch of plants, will be ok for the new pond.

How much do you feed them? That should give an idea of their current ammonia production. Keep in mind however that in a big pond they will likely grow considerably bigger.

4. Good point about the vertex..... i hadn't considered how long the settling time would be. A sieve is also an idea, but this is going to clog up quite quickly i suppose.... If i need two vertexs then i'm going to have to make the filter enclosure a bit bigger!

Make sure you have room for growth where you put your filters. Its probably still easy to do now, it could become a major headache if one day you decide you want koi and need extra filters.

As for a sieve, they basically never clog. Thats one thing that makes them so great. Waste is pushed down. Here is a clip showing one in action:
[ame]

 

[Andy41]

I hadn't consider mechanical sieving like that. Interesting. At what stage would you put it in the system? After the vertex i guess?

So if i add the skimmer as well, the system becomes :

retro drain - pump - skimmer input / vortex - sieve - bio1 - bio2 - return / bog

That video is really amazing. The water looks clean, but all that mechanical debris comes out of it.

cheers,

Andy.

 

[vertigo72]

A sieve could replace the vortex, it catches both floating and sinking debris. Perhaps you might still want a vortex or settling tank to let the smallest of particles sink (smaller than sand). Id put it after the sieve then, as the sieve would catch more. Ive never used one myself, but from what I read, its pretty much all you need as mechanical prefilter.